What differentiates extension from hyperextension?

What differentiates extension from hyperextension?
A.Extension bends joints in the opposite direction as hyperextension.
B.Extension straightens a joint, and hyperextension bends it but in the opposite direction from flexion.
C.Hyperextension straightens a joint, and extension bends it in the opposite direction from flexion.
D.Both bend joints, but extension can be damaging.