Katrina pushes off a flat sidewalk on her new skateboard.

What causes her to move?
A
The force of her push overcomes the forces of gravity and friction.

B
The force of gravity overcomes the forces of her push and friction.

C
The force of friction overcomes the normal force of the skateboard and the force of gravity.

D
The normal force of the skateboard overcomes the force of her push and the force of gravity.