When applying rigid-body mechanics to the study of human beings, the assumption made is Option B.The body does not deform by bending, stretching, or compressing.
Step-by-step explanation:
Rigid body mechanics is a body in which the gap between any two points will be constant in time, despite of external forces. The body cannot be deformed at any circumstances be it under application of any force. The forces acting over the body gets divided into two groups one is external, which shows the action of different bodies on the rigid body under force and internal force that binds the body together making it rigid. Body changes its motion only in case of pull against some external object.