Final answer:
The true statement is (C) An axe is made of a wedge and a lever. It is a compound machine, as it combines the function of both a wedge and a lever in its operation.
Step-by-step explanation:
The statement that is true among the options provided is: (C) An axe is made of a wedge and a lever. It is a compound machine. The reason this statement is correct is because an axe combines two simple machines: the sharp edge acts as a wedge to split material apart, while the handle functions as a lever to increase the force exerted during use. Therefore, an axe indeed is a compound machine consisting of both a wedge and a lever. For the other options: (A) A fixed pulley has a mechanical advantage of one, not three. (B) A block-and-tackle pulley is indeed attached to a support but this does not describe its functional characteristic fully, and other types of pulleys can also attach to supports. Hence, (C) is the accurate statement.