Which trial’s cart has the greatest momentum at the bottom of the ramp?

trial 1, because this trial has the greatest velocity
trial 2, because this trial has the greatest ramp height
trial 3, because this trial has a large mass and a large velocity
trial 4, because this trial has the greatest mass

The momentum of each cart is given by:

where
m is the mass of the cart
v is its velocity (at the bottom of the ramp)

To answer the problem, let's calculate the momentum of each of the 4 carts:
1)
2) 
3) 
4) 

Therefore, the cart with greatest momentum is cart 3, so the right answer is
- trial 3, because this trial has a large mass and a large velocity