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question_answer1) Three positive charges of equal value q are placed at vertices of an equilateral triangle. The resulting lines of force should be sketched as in
JEE Main Online Paper (Held On 26-May-2012)
A)
done
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B)
done
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C)
done
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D)
done
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question_answer2) In Young's double slit interference experiment, the slit widths are in the ratio 1: 25. Then the ratio of intensity at the maxima and minima in the interference pattern is
JEE Main Online Paper (Held On 26-May-2012)
A)
3:2
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B)
1:25
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C)
9:4
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D)
1:5
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question_answer3)
Which of the plots shown in the figure represents speed (v) of the electron in a hydrogen atom as a function of the principal quantum number (n)?
JEE Main Online Paper (Held On 26-May-2012)
A)
B
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B)
D
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C)
C
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D)
A
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question_answer4) A radio transmitter transmits at 830 kHz. At a certain distance from the transmitter magnetic field has amplitude \[4.82\times {{10}^{-11}}T.\]The electric field and the wavelength are respectively
JEE Main Online Paper (Held On 26-May-2012)
A)
0.014N/C, 36m
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B)
0.14N/C, 36m
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C)
0.14N/C, 360m
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D)
0.014N/C, 360m
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question_answer5) A satellite moving with velocity v in a force free space collects stationary interplanetary dust at a rate of\[\frac{dM}{dt}=\alpha v\] where M is the mass (of satellite t+ dust) at that instant. The instantaneous acceleration of the satellite is
JEE Main Online Paper (Held On 26-May-2012)
A)
\[-\frac{\alpha {{v}^{2}}}{2M}\]
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B)
\[-\frac{\alpha {{v}^{2}}}{M}\]
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C)
\[-\alpha {{v}^{2}}\]
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D)
\[-\frac{2\alpha {{v}^{2}}}{M}\]
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question_answer6) Currents of a 10 ampere and 2 ampere are passed through two parallel thin wires A and B respectively in opposite directions. Wire A is infinitely long and the length of the wire B is 2 m. The force acting on the conductor B, which is situated at 10 cm distance from A will be
JEE Main Online Paper (Held On 26-May-2012)
A)
\[8\times {{10}^{-5}}N\]
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B)
\[5\times {{10}^{-5}}N\]
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C)
\[8\pi \times {{10}^{-7}}N\]
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D)
\[4\pi \times {{10}^{-7}}N\]
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question_answer7) This question has Statement 1 and Statement 2. Of the four choices given after the Statements, choose the one that best describes the two Statements. Statement 1: It is not possible to make a sphere of capacity 1 farad using a conducting material. Statement 2: It is possible for earth as its radius is\[6.4\times {{10}^{6}}m.\]
JEE Main Online Paper (Held On 26-May-2012)
A)
Statement 1 is true, Statement 2 is true, Statement 2 is the correct explanation of Statement 1.
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B)
Statement 1 is false, Statement 2 is true.
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C)
Statement 1 is true, Statement 2 is true, Statement 2 is not the correct explanation of Statement 1.
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D)
Statement 1 is true, Statement 2 is false.
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question_answer8) The resistance of a wire is R. It is bent at the middle by 180° and both the ends are twisted together to make a shorter wire. The resistance of the new wire is
JEE Main Online Paper (Held On 26-May-2012)
A)
2R
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B)
R/2
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C)
R/4
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D)
R/S
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question_answer9) An air column in a pipe, which is closed at one end, will be in resonance with a vibrating tuning fork of frequency 264 Hz if the length of the column in cm is (velocity of sound = 330 m/s)
JEE Main Online Paper (Held On 26-May-2012)
A)
125.00
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B)
93.75
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C)
62.50
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D)
187.50
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question_answer10) The electrical resistance R of a conductor of length \[l\] and area of cross section a is given by\[R=\frac{\rho l}{a}\]where \['\rho '\]is the electrical resistivity. What is the dimensional formula for electrical conductivity' \['\sigma '\]which is reciprocal of resistivity?
JEE Main Online Paper (Held On 26-May-2012)
A)
\[[{{M}^{-1}}{{L}^{-3}}{{T}^{3}}{{A}^{2}}]\]
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B)
\[[M{{L}^{-3}}{{T}^{-3}}{{A}^{2}}]\]
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C)
\[[M{{L}^{-3}}{{T}^{-3}}{{A}^{-2}}]\]
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D)
\[[{{M}^{-2}}{{L}^{3}}{{T}^{2}}{{A}^{-1}}]\]
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question_answer11) The frequency of X-rays;\[\gamma \text{-}\]rays and ultraviolet rays are respectively a, b and c then.
JEE Main Online Paper (Held On 26-May-2012)
A)
\[a<b;b>c\]
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B)
\[a>b;b>c\]
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C)
\[a<b<c\]
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D)
\[a=b=c\]
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question_answer12)
The figure shows a combination of two NOT gates and a NOR gate. The combination is equivalent to a.
JEE Main Online Paper (Held On 26-May-2012)
A)
NAND gate
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B)
NOR gate
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C)
AND gate
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D)
OR gate
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question_answer13) Photoelectrons are ejected from a metal when light of frequency u falls on it. Pick out the wrong statement from the following.
JEE Main Online Paper (Held On 26-May-2012)
A)
No electrons are emitted if o is less than W/h, where W is the work function of the metal
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B)
The ejection of the photoelectrons is instantaneous.
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C)
The maximum energy of the photo electrons is\[h\upsilon .\]
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D)
The maximum energy of the photoelectrons is independent of the intensity of the light.
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question_answer14) The counting rate observed from a radioactive source at t = 0 was 1600 counts \[{{s}^{-1}}.\], and t = 8 s, it was 100 counts \[{{s}^{-1}}.\]. The counting rate observe das counts \[{{s}^{-1}}.\] at t = 6 s will be.
JEE Main Online Paper (Held On 26-May-2012)
A)
250
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B)
400
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C)
300
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D)
200
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question_answer15) A point particle is held on the axis of a ring of mass m and radius r at a distance r from its centre C. When released, it reaches C under the gravitational attraction of the ring. Its speed at C will be.
JEE Main Online Paper (Held On 26-May-2012)
A)
\[\sqrt{\frac{2Gm}{r}\left( \sqrt{2}-1 \right)}\]
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B)
\[\sqrt{\frac{Gm}{r}}\]
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C)
\[\sqrt{\frac{2Gm}{r}\left( 1-\frac{1}{\sqrt{2}} \right)}\]
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D)
\[\sqrt{\frac{2Gm}{r}}\]
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question_answer16)
A beam of light consisting of red, green and blue colours is incident on a right-angled prism on face AB. The refractive indices of the material for the above red, green and blue colours are 1.39, 1.44 and 1.47 respectively. A person looking on surface A C of the prism will see
JEE Main Online Paper (Held On 26-May-2012)
A)
no light
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B)
green and blue colours
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C)
red and green colours
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D)
Red colour only
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question_answer17)
The force \[\overset{\to }{\mathop{F}}\,=F\hat{i}\] on a particle of mass 2 kg, moving along the x-axis is given in the figure as a function of its position x. The particle is moving with a velocity of 5 m/s along the x-axis at x = 0. What is the kinetic energy of the particle at\[x=8m?\]
JEE Main Online Paper (Held On 26-May-2012)
A)
34J
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B)
34.5 J
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C)
4.5J
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D)
29.4J
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question_answer18) The door of a working refrigerator is left open in a well insulated room. The temperature of air in the room will
JEE Main Online Paper (Held On 26-May-2012)
A)
decrease
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B)
increase in winters and decrease in summers
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C)
remain the same
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D)
increase
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question_answer19) The terminal velocity of a small sphere of radius a in a viscous liquid is proportional to
JEE Main Online Paper (Held On 26-May-2012)
A)
\[{{a}^{2}}\]
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B)
\[{{a}^{3}}\]
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C)
a
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D)
\[{{a}^{-1}}\]
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question_answer20) A stone of mass m, tied to the end of a string, is whirled around in a circle on a horizontal frictionless table. The length of the string is reduced gradually keeping the angular momentum of the stone about the centre of the circle constant. Then, the tension in the string is given by \[T=A{{r}^{n}},\]where A is a constant, r is the instantaneous radius of the circle. The value of n is equal to.
JEE Main Online Paper (Held On 26-May-2012)
A)
-1
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B)
-2
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C)
-4
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D)
-3
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question_answer21) The disturbance y (x, t) of a wave propagating in the positive x-direction is given by \[y=\frac{1}{1+{{x}^{2}}}\] at time t = 0 and by \[y=\frac{1}{\left[ 1+{{\left( x-1 \right)}^{2}} \right]}\]at t = 2 s, where x and y are in meters. The shape of the wave disturbance does not change during the propagation. The velocity of wave in m/s is.
JEE Main Online Paper (Held On 26-May-2012)
A)
2.0
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B)
4.0
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C)
0.5
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D)
1.0
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question_answer22) An ideal monatomic gas with pressure P, volume V and temperature T is expanded isothermally to a volume 2V and a final pressure \[{{P}_{i}}.\] If the same gas is expanded adiabatically to a volume 2V, the final pressure is \[{{P}_{a}}.\]The ratio \[\frac{{{P}_{a}}}{{{P}_{i}}}\]is.
JEE Main Online Paper (Held On 26-May-2012)
A)
\[{{2}^{-1/3}}\]
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B)
\[{{2}^{1/3}}\]
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C)
\[{{2}^{2/3}}\]
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D)
\[{{2}^{-2/3}}\]
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question_answer23) A telescope of aperture \[3\times {{10}^{-2}}m\] diameter is focused on a window at 80 m distance fitted with a wire mesh of spacing \[2\times {{10}^{-3}}m\]. Given:\[\lambda =5.5\times {{10}^{-7}}m,\]which of the following is true for observing the mesh through the telescope?
JEE Main Online Paper (Held On 26-May-2012)
A)
Yes, it is possible with the same aperture size.
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B)
Possible also with an aperture half the present diameter.
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C)
No, it is not possible.
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D)
Given data is not sufficient.
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question_answer24) This question has Statement 1 and Statement 2. Of the four choices given after the Statements, choose the one that best describes the two Statements. Statement 1: A charged particle is moving at right angle to a static magnetic field. During the motion the kinetic energy of the charge remains unchanged. Statement 2: Static magnetic field exert force on a moving charge in the direction perpendicular to the magnetic field.
JEE Main Online Paper (Held On 26-May-2012)
A)
Statement 1 is false, Statement 2 is time.
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B)
Statement 1 is time, Statement 2 is time, Statement 2 is not the correct explanation of Statement 1.
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C)
Statement 1 is true. Statement 2 is false.
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D)
Statement 1 is time, Statement 2 is time, Statement 2 is the correct explanation of Statement 1.
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question_answer25) A ball is dropped vertically downwards from a height h above the ground. It hits the ground inelastically and bounces up vertically. Neglecting subsequent motion and air resistance, which of the following graph represents variation between speed (v) and height (h) correctly?
JEE Main Online Paper (Held On 26-May-2012)
A)
done
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B)
done
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C)
done
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D)
done
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question_answer26) A thick-walled hollow sphere has outside radius\[{{R}_{0}}.\]It rolls down an incline without slipping and its speed at the bottom is \[{{v}_{0}}.\].Now the incline is waxed, so that it is practically frictionless and the sphere is observed to slide down (without any rolling). Its speed at the bottom is observed to be\[5{{v}_{0}}/4.\]The radius of gyration of the hollow sphere about an axis through its centre is.
JEE Main Online Paper (Held On 26-May-2012)
A)
\[3{{R}_{0}}/2\]
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B)
\[3{{R}_{0}}/4\]
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C)
\[9{{R}_{0}}/16\]
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D)
\[3{{R}_{0}}\]
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question_answer27)
In a cylindrical water tank, there are two small holes A and B on the wall at a depth of\[{{h}_{1}},\] from the surface of water and at a height of \[{{h}_{2}}\] from the bottom of water tank. Surface of water is at height of\[{{h}_{2}}\] from the bottom of water tank. Surface of water is at height H from the bottom of water tank. Water coming out from both holes strikes the ground at the same point S. Find the ratio of \[{{h}_{1}}\]and \[{{h}_{2}}\]
JEE Main Online Paper (Held On 26-May-2012)
A)
Depends on H
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B)
1:1
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C)
2:2
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D)
1:2
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question_answer28) This question has Statement 1 and Statement 2. Of the four choices given after the Statements, choose the one that best describes the two Statements. Statement 1: If you push on a cart being pulled by a horse so that it does not move, the cart pushes you back with an equal and opposite force. Statement 2: The cart does not move because the force described in statement 1 cancel each other.
JEE Main Online Paper (Held On 26-May-2012)
A)
Statement 1 is time, Statement 2 is time, Statement 2 is the correct explanation of Statement 1.
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B)
Statement 1 is false, Statement 2 is time.
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C)
Statement 1 is true. Statement 2 is false.
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D)
Statement 1 is time. Statement 2 is time, Statement 2 is not the correct explanation of Statement 1.
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question_answer29) In an experiment of potentiometer for measuring the internal resistance of primary cell a balancing length \[\ell \]is obtained on the potentiometer wire when the cell is open circuit. Now the cell is short circuited by a resistance R, If R is to be equal to the internal resistance of the cell the balancing length on the potentiometer wire will be.
JEE Main Online Paper (Held On 26-May-2012)
A)
\[\ell \]
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B)
\[2\ell \]
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C)
\[\ell /2\]
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D)
\[\ell /4\]
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question_answer30) The capacitor of an oscillatory circuit is enclosed in a container. When the container is evacuated, the resonance frequency of the circuit is 10 kHz. When the container is filled with a gas, the resonance frequency changes by 50 Hz. The dielectric constant of the gas is.
JEE Main Online Paper (Held On 26-May-2012)
A)
1.001
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B)
2.001
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C)
1.01
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D)
3.01
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