Which of these physical settings makes sense for an object moving along the x-axis? Its position at any time is given by x(t) = 3cos(π t) + 2

a. A skydiver falling from a plane, before she opens her parachute.
b. The shadow cast by a rock that's stuck on the edge of a spinning wheel.
c. A car driving from San Diego to Los Angeles.
d. An ant walking at a steady pace from the tip of a propeller toward the hub.
e. None of these settings.