Which has the larger change in momentum 
This is a concept question in my physics class, It isn't for marks, its just to gauge your understanding of the subject. I'm not sure if I have the right idea. 
since the mass of block A is 4 times larger, it would have a much slower change in velocity compared to bock B. Does this mean it would have a smaller change in momentum?
 A: From definition, force is a momentum change rate in time $\vec{F} = \frac{\text{d}\vec{p}}{\text{d}t}$. So if the force working on both is equal then their momentum change would be the same so answer C, but... in my opinion the correct answer is D. There is no information given about friction (if we assume that blocks are moved on surface), whether is or is not. If there is friction, which is proportional to weight, it will reduced total force on the blocks, and momentum rate will change, it will be lower for block A than for B. So in case of friction, answer B is correct. And there is resistance of the medium in which blocks are moving, which here is independent of shape which is the same, but resistance is proportional to the speed and therefore to momentum.
A: A constant force pushes a mass $m$ along a distance $x$. What is the final velocity? The acceleration is $a=\frac{F}{m}$ and the kinematic relationship between speed and distance is
$$ \left. x = \frac{v^2}{2 a} \right\} v = \sqrt{2 a x} = \sqrt{ 2 \frac{F}{m} x}$$
The final momentum is 
$$ p = m v = \sqrt{2 F x m} $$
So momentum is proportional to $\sqrt{m}$ in this case.
