Which of the following is NOT a function of muscles?

The correct answer highlights that the protection of blood cells is not a primary function of muscles. Muscles are primarily responsible for facilitating movement, stabilizing joints, and maintaining posture.

Muscles enable locomotion by contracting and relaxing, which allows the body to move. They also play a vital role in stabilizing joints by providing support and control during various activities, preventing injuries, and allowing for a wide range of movements. Furthermore, muscles maintain posture by continually adjusting to keep the body upright against the force of gravity.

While muscles contribute to overall health and function, they do not directly protect blood cells. The protection of blood cells is primarily the role of the skeletal system (through bone marrow, where many blood cells are produced) and the immune system (which protects against pathogens that may affect blood cells).