Which of the following is not in equilibrium? [Physics: Force]

A. A book at rest on a table.
B. A car sitting still despite the fact that there is a person trying hard to push it out of a pit.
C. A baseball flying through the air along a perfectly parabolic trajectory.
D. A hockey puck sliding at a constant speed along perfectly frictionless ice.

Thanks. 10 points to best answer!

I'm pretty sure it's C for the first one, and the last two are both A.