A bobsledder pushes her sled across horizontal snow to get it going, then jumps in. After she jumps in, the sled gradually slows to a halt. What forces act on the sled just after she's jumped in?
a) Gravity and kinetic friction
b) Gravity and normal force
c) Gravity and the force of the push
d) Gravity, a normal force, and kinetic friction
e) Gravity, a normal force, kinetic friction, and the force of the push