Which Statement Regarding Levers in Movement Is True

Which statement regarding levers in movement is true?

A) An axis of movement and a single source of force are required to establish a lever.
B) For a basic lever, usually there are two external or two internal forces.
C) In the human body, levers usually involve a single force and axis of motion.
D) Levers are utilized in the body when an external force is countered or controlled by muscle force.