Angle of descent of cam is defined as the angle__________________?

A. during which the follower returns to its initial position
B. of rotation of the cam for a definite displacement of the follower
C. through which the cam rotates during the period in which the follower remains in the highest position
D. moved by the cam from the instant the follower begins to rise, till it reaches its highest position
E. moved by the cam from beginning of ascent to the termination of descent