The correct option is A stapedius
The stapedius is the smallest skeletal muscle in the human body, at just over one millimeter in length.
The masseter muscle is a facial muscle that plays a major role in the chewing of solid foods.
Stapes is a stirrup-shaped bone in the middle ear. It is supposed to be the smallest bone in the human body.
The gluteus maximus is the main extensor muscle of the hip.