Aproton, a deuteron (a hydrogen nucleus containing one proton and one neutron), and an alpha particle (a helium nucleus consisting of two protons and two neutrons) initially at rest are all accelerated through the same distance in the uniform electric field created by a very large charged plate. compare their final kinetic energies.

I think I'll back into this answer in a slightly crooked but totally legitimate way:

-- The final kinetic energy of each item is exactly the work done on it by the field, as it moves the distance to the finish line.

-- The work done by the field is (force on the particle) x (distance it moves) .

-- They all move the same distance, so their kinetic energies line up in the same order as the forces that the field exerts on them.

-- The force exerted on each item by the electric field depends only on the net charge of each item.

. . . the proton ==>  charge = +1

. . . the deuteron ==>  charge = +1

. . . the alpha particle ==>  charge = +2

So . . . . .

-- The field does the same amount of work on the proton and the deuteron.  Their kinetic energies are equal when they reach the finish line.  But the deuteron gets there later than the proton, with lower speed, on account of its larger mass and lower acceleration.  

-- The field does more work on the alpha particle.  It has more mass than either of the others, so its acceleration is the least of all, and it's the last one to cross the finish line.  But once it gets there, it has the greatest kinetic energy.

Order of arrival:

#1 to win ... proton

#2 to place ... deuteron

#3 to show ... alpha particle

Kinetic energy at the finish:

least ... proton/deuteron (tied)

most ... alpha particle

hypothesising or postulating

answer: a. same unit

explanation: