For Question 1, the best choice for increasing the net force on the cart is:
Applying a braking force by dragging your foot.
This is because applying a braking force introduces an unbalanced force on the cart, which alters its state of motion, potentially increasing the net force acting on it.
For Question 2, the correct response is:
All the forces acting on the cart equal zero net force.
This is because a cart moving at constant velocity indicates that the net force acting on the cart is zero, meaning that all the forces are balanced.