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SRJC 2010 9646/Prelim/2010

SERANGOON JUNIOR COLLEGE General Certificate of Education Advanced Level Higher 2

PHYSICS 9646

Preliminary Examination 26 August 2010 Paper 1 Multiple Choice 1 hour 15 minutes

Additional Materials: Optical Mark Sheet (OMS) READ THIS INSTRUCTIONS FIRST

Write your name, civics group and index number in the spaces at the top of this page. There are forty questions on this paper. Answer all questions. For each question, there are four possible answers labeled A, B, C and D. Choose the one you consider correct and record your choice in soft pencil on the OMS. Read the instructions on the OMS very carefully. Each correct answer will score one mark. A mark will not be deducted for a wrong answer. Any rough working should be done in this question paper.

This document consist of 21 printed pages and 1 blank page

For Examiner’s Use

Section A

Total / 40

NAME

CG INDEX NO.

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SRJC 2010 9646/Prelim/2010

DATA AND FORMULAE Data

speed of light in free space, c = 3.00 x 108 m s1

permeability of free space, 0 = 4 x 107 H m1

permittivity of free space, 0 = 8.85 x 1012 F m1

(1 / (36π)) x 109 F m1

elementary charge, e = 1.60 x 1019 C

the Planck constant, h = 6.63 x 1034 J s

unified atomic mass constant, u = 1.66 x 1027 kg

rest mass of electron, me = 9.11 x 1031 kg

rest mass of proton, mp = 1.67 x 1027 kg

molar gas constant, R = 8.31 J K1 mol1

the Avogadro constant, NA = 6.02 x 1023 mol1

the Boltzmann constant, k = 1.38 x 1023 J K1

gravitational constant, G = 6.67 x 1011 N m2 kg2

acceleration of free fall, g = 9.81 m s2

Formulae uniformly accelerated motion, s = ut + ½ at2

v2 = u2 + 2as

work done on/by a gas, W = pV

hydrostatic pressure, p = gh

gravitational potential, = –

displacement of particle in s.h.m., x = x0 sin t

velocity of particle in s.h.m., v = vo cost

v =

resistors in series, R = R1 + R2 + … resistors in parallel, 1/R = 1/R1 + 1/R2 + …

electric potential, V = Q / 4or

alternating current/voltage, x = x0sin t

transmission coefficient, T α exp(2kd)

where k =

radioactive decay, x = x0 exp(t)

decay constant, =

r

Gm

22

0 xxω

2

2

h

E)m(U8 π

21

693.0

t

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SRJC 2010 9646/Prelim/2010

1 In a speed test, an engineer has determined the top speed of an automobile to be

240.57 km h-1. The accuracy of his equipment is ±5%.

Which of the following is the correct representation of his results?

A (241 ± 2) km h-1 B (240 ± 10) km h-1

C (241 ± 12) km h-1 D (240.57 ± 12.03) km h-1

Ans: B

V/V = 0.05

V = 0.05 x 240.57

= 10 km h-1

V = (240 ± 10) km h-1

2 A certain particle is travelling at a uniform velocity of 20 m s-1. From t = 2 s onwards, it

decelerates uniformly to 5 m s-1, in 40.0 m.

From t = 0 s, what is the distance needed for the particle to come to rest if it continues at the

same uniform deceleration?

A 2.7 m B 22.7 m C 42.7 m D 82.7 m

Ans: D

v2 = u2 + 2as

52 = 202 + 2a(40)

a = -4.688 m s-2

v2 = u2 + 2as

02 = 52 + 2(-4.688)s

s = 2.666 m

Total distance needed = (20)(2) + 40 + (2.666) = 82.7 m

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SRJC 2010 9646/Prelim/2010 [Turn Over

3 The figure below shows the acceleration-time graph of an object moving in the positive

direction.

Which of the following statements best describes what is happening to the object from

t = 3 s to t = 10 s?

A The object is slowing down at a slower rate as time passes

B The object is slowing down at a faster rate as time passes

C The object is speeding up at a slower rate as time passes.

D The object’s speed remains constant as time passes.

Ans: C

4 A heavy metal ball suspended from an elastic string is fully immersed in oil in a beaker,

resting on a scale balance.

The force that the ball exerts downwards on the oil in the beaker forms an action-reaction

pair with

A the weight of the metal ball

B the average tension in the string

C the Archimedean upthrust on the object

D the force which the oil-filled beaker exerts on the scale balance

Ans: C

When the ball exerts a force downwards on the oil, the oil reacts by exerted an equal and

opposite force upwards on the ball. This upward force is the upthrust.

a / m s-2

0 t / s 10 3

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SRJC 2010 9646/Prelim/2010

5 Alice, whose actual weight is 540 N, registers to her delight, a reading of 500 N on a

weighing machine, when she is in the lift of the five-star hotel she is staying in.

Which of the following situations is happening?

A The lift is decelerating and moving upwards

B The lift is accelerating and moving upwards

C The lift is decelerating and moving downwards

D The lift is moving with a constant velocity.

Ans: A

N – mg = ma

N = m(g + a)

N = mg + ma

Alice’s actual weight = mg

Thus, ma has to be negative, a is negative.

i.e. a is opposite to assumed upwards direction.

6 What volume of a 300 cm3 ice is above water that has a density of 1.0 g cm-3? The ice has a

density of 0.9 g cm-3.

A 15 cm3 B 30 cm3 C 270 cm3 D 300 cm3

Ans: B

Weight of ice = upthrust of water on ice

ρiVig = ρwVxg, where Vx = volume of ice below water

Let volume of ice above water = Vy, then Vi = Vx + Vy

ρiVig = ρw(Vi - Vy)g

Vi =

wi

w

iV

= 1.0 0.9

(300)1.0

= 30 cm3

N, normal contact force between Alice and floor of lift

mg

Alice

a

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SRJC 2010 9646/Prelim/2010 [Turn Over

7 Which of the following correctly describes the situation where an object is floating in a body

of liquid correctly?

The weight of liquid which would occupy a volume equal to the volume of the object

A must be equal to the weight of the object

B below the fluid surface must be equal to the weight of the object below the fluid surface

C below the fluid surface must be equal to the weight of the object

D above the fluid surface must be equal to the weight of the object below the fluid surface

Ans: C

8 A car is moving upwards along a slope with a constant speed.

Which of the following statements best describe the conversion of energy taking place?

The energy output from the engine is transformed into

A an increase in gravitational potential energy of the car.

B an increase in gravitational potential energy and kinetic energy of the car.

C an increase in gravitational potential energy as well as work done against resistive

forces.

D an increase in gravitational potential energy and kinetic energy of the car, as well as

work done against resistive forces.

Ans C

Energy from the engine is not used to transform into kinetic energy as there is no gain in the

kinetic energy. The energy is transformed into an increase in gravitational potential energy as

well used to do work against the frictional forces.

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SRJC 2010 9646/Prelim/2010

9 An object is pushed from rest in a straight line by a variable force F along a rough ground.

The ground exerts a constant frictional force of 5 N throughout the motion of the object. The

graph of how the variable force F varies with displacement x is shown below.

The magnitude of the kinetic energy of the object when it has travelled 10 m is

A the area K.

B the area K + L.

C the area K + L + M.

D impossible to obtain as mass of object is not given.

Ans A

Gain in KE = Net Work Done

= Area under resultant force – time graph

= Area K

F / N

x / m

K

L M

10

5

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SRJC 2010 9646/Prelim/2010 [Turn Over

10 A metal sphere is hanging on a string. The metal sphere is then swung around in a horizontal

circle as shown.

Which of the following shows the correct free-body diagram of the sphere at this instance?

A B

C D

Ans: D

11 Which of the following statement is true for an object in horizontal circular motion with

constant angular velocity?

A The kinetic energy remains constant.

B The kinetic energy and linear momentum remain constant.

C The linear velocity does not vary.

D Acceleration remains constant.

Ans: A. The kinetic energy remains constant.

Tension

Weight

Centripetal force

Tension

Weight

Centripetal force

Weight

Centripetal force Tension

Weight

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SRJC 2010 9646/Prelim/2010

12 The distance between a point, X, in space and the centre of the Earth is 25 times the radius

of Earth. The gravitational field strength due to Earth at that point is

A 1.56 x 10-2 N kg-1. B 1.57 x 10-2 N kg-1.

C 3.90 x 10-1 N kg-1. D 3.92 x 10-1 N kg-1.

Ans: B

gX =

2E

X

GM

r ……….. (1)

Since gE =

2E

E

GM

r gE (rE)2 = GME

Hence from (1) : gX =

2

225

E E

E

g r

r=

9.81

625= 1.57 x 10-2 N kg-1

13 A satellite in orbit encounters significant friction and spirals gradually to Earth.

Which of the following statements is correct?

A The satellite gains gravitational potential energy.

B The satellite loses kinetic energy.

C The total energy (gravitational potential energy and kinetic energy) of the satellite

remains constant.

D The total energy (gravitational potential energy and kinetic energy) of the satellite

decreases.

Ans: D

A satellite spirals towards Earth when it encounters significant resistance in the atmosphere.

The satellite’s total energy decreases because some of the energy is converted to heat. As

the satellite falls, its gravitational potential energy reduces while its kinetic energy increases.

14 The total energy of a horizontal oscillating mass spring system is doubled. This will cause its

amplitude to

A increase by 2 . B increase by 2.

C increase by 2 2 . D increase by 4.

Ans: A

TE = 21

2kA

Therefore,

21

1

222

1

2 1

2

kATE

TEkA

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SRJC 2010 9646/Prelim/2010 [Turn Over

21 1

21 2

2

TE A

TE A

2 212 1

1

2

TEA A

TE

2 1 2A A

15 A toy car moving along a horizontal plane in simple harmonic motion starts from the

amplitude at t = 0 s. If the amplitude of its motion is 5.00 cm and frequency is 2.00 Hz, the

magnitude of the acceleration of the toy car at 1.7 s is

A 0.25 m s-2 B 0.51 m s-2

C 1.60 m s-2 D 6.40 m s-2

Ans: D

x = x0 cos (ωt)

= 5.00 cos (4.00π (1.7))

= - 4.05 cm

a = 2ω x = (4π)2(4.05 x 10-2) = 6.40 m s-2

16 An ideal gas underwent an isothermal expansion from state A to state B, followed by an

isobaric expansion from state B to state C and an adiabatic contraction from state C back to

state A.

Which of the following is a correct description of the net work done by the ideal gas after

completing one full cycle of the above process?

A Net work done by gas is zero because the gas returns to its initial state.

B Net work done by gas is positive because there is a net heat loss during isobaric

expansion and no heat lost during isothermal and adiabatic process.

C Net work done by gas is negative because the gas expands through two processes

and contracts in one process only.

D Net work done on gas is positive because the adiabatic process occurs at a higher

average pressure than the other two processes.

Ans: D

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SRJC 2010 9646/Prelim/2010

17 3.0 mol of ideal gas at an initial pressure of 6.0 x 10-5 Pa expanded to 3 times its original

volume while the temperature reduced by half, from 20 ۫C to 10 ۫C.

What is the final pressure of the gas?

A 1.00 x 10-5 Pa B 1.74 x 10-5 Pa

C 1.93 x 10-5 Pa D 2.07 x 10-5 Pa

Ans: C

5283151 93 10

3 29315 Pa

( ) ( )

.( ) ( ) .

.

i f

fif i i

f i

pV nRT

pV pV

T T

TV VP P P

V T V

18 The diagram shows two waves X and Y.

Wave Y has amplitude 8 cm and frequency 150 Hz.

What are the possible amplitude and frequency of wave X?

amplitude / cm frequency / Hz

A 4 50

B 4 450

C 16 50

D 16 450

Ans: C

Since there are three complete cycle of wave Y in wave X for the same time duration, hence

frequency of wave X is one third that of wave Y, i.e. 150/3 = 50 Hz.

And its amplitude is twice that of wave Y so wave X amplitude

= 8 x 2 = 16 cm.

displacement

0

Wave X Wave Y

time

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SRJC 2010 9646/Prelim/2010 [Turn Over

19 Light can exhibit all of the phenomena listed.

Which phenomenon can sound not exhibit?

A interference B polarisation

C refraction D total internal reflection

Ans: B

Sound waves are longitudinal waves. Hence polarisation is not evident in sound waves.

20 The diagram shows a standing wave on a string. The standing wave has three nodes N1, N2

and N3.

Which statement is correct?

A All points on the string vibrate in phase.

B All points on the string vibrate with the same amplitude.

C Points equidistant from N2 vibrate with the same frequency and in phase.

D Points equidistant from N2 vibrate with the same frequency and the same amplitude.

Ans: D

A standing wave will have particles in phase with each other in a loop and in anti phase with

particles in the adjacent loop. Hence the particles equidistant from N2 would only have equal

amplitude and not similar phase.

21 A beam of monochromatic light of wavelength 550 nm is incident normally on a diffraction

grating that has 300 lines per mm.

What is the total number of images produced by light transmitted through this grating?

A 6 B 7 C 12 D 13

Ans: d = 31 10

300

x

= 3.33 x 10-6 m

d sin θ = nλ

For maximum images sin θ = 1

n = d

=

6

9

333 10

550 10

x

x

-

-

.= 6.06

Hence max no of images = 2 x 6 + 1 = 13

N1 N2 N3

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SRJC 2010 9646/Prelim/2010

22 3 charges X, Y and Z of charge 3.2 x 10-16 C, -1.4 x 10-16 C and -0.8 x 10-16 C respectively,

are placed at the corners of an equilateral triangle of sides 1.7 cm long, as shown below.

What is the electric potential at position of charge Y due to X and Z?

A 7.47 x 10-3 V B 1.27 x 10-4 V

C 2.12 x 10-4 V D 1.78 x 10-20 V

Ans: B

16 16 4

0

13 2 10 0 8 10 1 27 10

4 V( . . ) .V

r

23 Two large parallel plates are situated 50 mm apart as shown. The potential difference

between the plates is +V.

A unit positive charge moves from X to Y.

Which graph shows the variation of electric potential energy U of the unit positive charge with

respect to the distance s measured perpendicularly from the plate of zero potential as the

charge moved from X to Y?

A B

C D

X

Z Y

1.7 cm

U

s

U

s

U

s

U

s

50 mm

10 mm

X + V 0 V

Y

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SRJC 2010 9646/Prelim/2010 [Turn Over

Ans: A

As field strength is constant, dV

dsis a constant and hence, the gradient is constant and the

graph is a straight line graph which does not pass through the origin.

24 Four identical lamps are powered by an e.m.f source.

Which of the following will cause the batteries to use up all its energy in the shortest time?

The bulbs are

A all arranged in parallel.

B all arranged in series.

C arranged in combination of series and parallel.

D arranged such that there are an equal number of lamps arranged in series and parallel.

Ans: A. The lamps will be brightest when they are all arranged in parallel.

25 Which of the following statements is true about the e.m.f. of a cell?

A It is the electrical force required to move a unit charge within a circuit.

. B It is the electrical power changed into other forms per unit charge within the cell.

C It is the electrical energy supplied per unit current by the cell.

D It is the electrical energy supplied per unit charge by the cell.

Ans: D. It is the electrical energy supplied per unit charge by the cell.

26 Jackie arranged a circuit setup as shown below. The ideal voltmeter reads 7 V when J1 is

closed and J2 is opened. The voltmeter reads 9 V when J2 is closed and J1 is opened.

What will the voltmeter reading be when both J1 and J2 are closed?

A 4.55 V B 4.70 V C 4.85 V D 5.05 V

Ans: C

Let e.m.f. of source be E and internal resistance of source be r

Scenario 1: J1 closed and J2 open:

7= 2

2 rx E ------------------------(1)

V

J1 J2

2 Ω 3 Ω

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SRJC 2010 9646/Prelim/2010

Scenario 2: J1 open and J2 closed:

9 = 3

3 rx E ------------------------(2)

9 3 2

7 3 2

r

r

18 (3+r) = 21 (2+r)

54 + 18r = 42 + 21r

3r = 12

r = 4 Ω subst in (1)

7 = 2

2 4x E

E = 21 V

Scenario 3: J1 closed and J2 closed:

Total resistance (not including the internal resistance) = 2 3 6

2 3 5

Voltmeter reading = 1

6

5 26

45

= 4.85 V

27 An 18 V battery of negligible internal resistance connected to a potentiometer X of total

resistance 150 Ω as shown below. Filament lamps L1 and L2 are connected as shown with

the sliding contact positioned such that there is equal division of the resistance of X. Both

lamps are marked ‘9 V, 27 W’.

Which of the following will be observed when switch S is closed?

A L1 will not be as bright as L2

B L1 will remain as bright as before.

C L1 will be dimmer than before S was closed.

D L1 will be brighter than before S was closed.

Ans: D

18 V

L1

X = 150 Ω

L2

S

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SRJC 2010 9646/Prelim/2010 [Turn Over

2 29

27

VR

P = 3 Ω

Scenario 1: Switch S open

Potential difference across L1 much less than 9 V because effective resistance is much less

than 75 Ω. L1 is dim.

Scenario 2: Switch S closed

Potential difference across L1 will be 9 V, and across L2 will also be 9 V. Both lamps will have

the normal brightness.

28 An electric charge present in a magnetic field of experiences a non-zero magnitude constant

force when

A the charge moves at an oblique angle to the magnetic field lines with constant speed.

B the charge moves perpendicular to the magnetic field lines with increasing speed.

C the charge moves in the same direction as the magnetic field lines with constant

speed.

D the charge moves in the same direction as the magnetic field lines with increasing

speed.

Ans: A.

L1

18 V

75 Ω 75 Ω

3 Ω

L1

18 V

75 Ω 75 Ω

3 Ω

L2

3 Ω

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SRJC 2010 9646/Prelim/2010

29 The forces between two parallel wires with current flowing

A in the same direction causes the wires to attract.

B in the same direction causes the wires to repel.

C is independent of the current directions.

D is in a direction that depends on the magnitude of the currents.

Ans: A. The force between two parallel wires with current flowing in the same direction

causes the wire to attract.

30 A student uses a long copper wire to form a square coil with side 7 cm of 50 turns. He places it such that it is perpendicular to a magnetic field. The flux density of the field is changed from 10 mT to 60 mT in 2.0 s.

What is the average e.m.f. induced in the coil?

A 6.1 mV B 7.4 mV

C 12 mV D 74 mV

Ans: A. A = 0.07 x 0.07 = 0.0049

e.m.f. = N/t = 50 x 0.0049 x (60 - 10) x 10-3 / 2.0 = 6.1 mV

31 Which of the following lists are all forms of conservation of energy?

A First Law of thermodynamics, Lenz’s Law and Conservation of linear momentum.

B First Law of thermodynamics, Lenz’s Law and Einstein’s photoelectric equation

C Lenz’s Law, Einstein’s photoelectric equation and Conservation of linear momentum.

D First Law of thermodynamics, Einstein’s photoelectric equation and Conservation of

linear momentum.

Ans: B

32 A varying d.c. current is passed through a certain resistor as shown below.

The r.m.s value of the given current is

A 4.10 A B 5.80 A C 8.49 A D 16.8 A

Ans: A

0

2.0

4.0

6.0

I / A

t / s 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0 20.0

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SRJC 2010 9646/Prelim/2010 [Turn Over

Area = [(16.0 x 8.0) + (20.0 x 2.0)] = 168

.

.

area under graph for one periodroot-mean-square e.m.f

one period

168

10 0

4 10 V

33 The output voltage of a certain generator is V = V0 sin 2πft. The frequency f and the

amplitude V0 are directly proportional to one another. The generator is connected to a

resistor.

When the frequency is varied, the instantaneous peak power developed in the resistor is

A proportional to f2

B proportional to f

C inversely proportional to f2

D inversely proportional to f

Ans: A

Peak power, 2

00

VP

R

Since 0 ,V f

2

0 f

PR

0

I2/A2

t / s 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0 20.0

4.0

16.0

36.0

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SRJC 2010 9646/Prelim/2010

34 In a typical photoelectric effect experiment, monochromatic light is irradiated onto a metal

surface. The graph below shows the results of how y varies with x.

What is y and x?

y x

A p.d across emitter and collector frequency of radiation

B Intensity of source frequency of radiation

C photocurrent intensity of source

D photocurrent p.d across emitter and collector

Ans D

35 The intensity of a beam of monochromatic light is halved. Which one of the following

represents the corresponding change if any in the momentum of each photon of the radiation?

A halved B one quarter of original

C the same D doubled

Ans C

By de Broglie’s equation

p = h

.

However, changing the intensity of the light source does not change any of the variables in

the equation, therefore the momentum of the photon is unchanged.

36 The maximum energy of photons emitted from an X-ray tube is certain to be decreased by

A using a target metal with a higher atomic number.

B decreasing the voltage across the tube.

C cooling the metal target.

D using a target metal with a larger interatomic spacing.

Ans B

The maximum energy of photons emitted is emitted when all the KE of an incident electron is

transformed into a E-M radiation.

The KE of the electrons is reduced when the voltage across the tube is decreased.

x

y

0

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SRJC 2010 9646/Prelim/2010 [Turn Over

37 An electron has kinetic energy of 0.5 MeV. If its momentum is measured with an uncertainty

of 1.00 %, what is the minimum uncertainty in its position?

A 1.38 1011 m B 1.38 1012 m

C 3.30 1020 m D 3.30 1021 m

Ans A

0.5 x 106 x 1.6 x 10-19 = ½ mv2

½ mv2 = (0.5)( 9.11 x 1031) v2

v = 419.08 x 106 m s-1

p = mv = ( 9.11 x 1031)( 419.08 x 106) = 3.818 x 10-22

Δp = 3.818 x 10-22 x .1 00

100 = 3.818 x 10-24

Using Heisenberg’s uncertainty principle, 2

x p

-34

-11

-24

6.63×10

2= =1.38×10 m

2 2×3.818×10x

p

π

38 Which of the following statements about a semiconductor diode in reversed-bias is correct?

A The p-type material of the diode is connected to the positive terminal of the source of

e.m.f.

B Electrons in the n-type side of the diode will cross steadily to the p- type side.

C The applied potential difference from the source of e.m.f. reinforces the junction

potential.

D The depletion layer is reduced.

Ans C

39 The half-life of 219

86 Rn is 4.0 s.

What is the activity after 3.4 s when the initial sample size at time t = 0 s is 1.5 mol of 219

86 Rn?

A 0.144 Bq B 8.68 x 1022 Bq

C 1.33 x 1023 Bq D 7.68 x 1023 Bq

Ans: B

0

23

0 0

23 4

23 224

6 02 10 1 5

6 02 10 1 5 8 68 10ln

( . )

( . . )

( . . ) .

tA A e

A N

A e Bq

21

SRJC 2010 9646/Prelim/2010

40 238

92U decays through a series of transformation. It underwent one α-emission, two β-

emissions and one γ-emission.

Which of the following is the final product of this series of transformation?

A 236

91Pa B 234

92U C 238

92U D 234

93 Np

Ans: A

238 234 4 0 0

92 92 2 1 02U U