The Fact That the Pectoralis Major Can Adduct the Arm

Multiple Choice

The fact that the pectoralis major can adduct the arm at the shoulder joint when the arm is in anatomic position but abduct the arm if it is already abducted above 100 degrees is an example of the:

A) muscle being stronger above 100 degrees
B) all-or-none response law
C) changing line of pull of the muscle relative to the joint
D) sliding filament mechanism