Which of the following statements describes a compound machine?
a. it has movement in only one direction.
b. it can only be acted on by one force.
c. it is made up of more than one simple machine.
d. it makes work more difficult.

The answer is letter C.

Compound machines are structurally built or made with more than one simple machine. A good example of this is the wheelbarrow, which consists of a lever, an axle, and a wheel. These are different simple machines that when bound together can help us perform difficult tasks (e.g. lifting or transferring heavy loads).  

The answer to the question is c.