The musculoskeletal system refers to the following components.

• A. Involuntary muscles of the nervous system.
• B. Bones and voluntary muscles of the body.
• C. Nervous system's control over the muscles.
• D. Connective tissue that supports the skeleton.

Answer: (B)

The musculoskeletal system is defined by bones and skeletal (voluntary) muscles, which provide the body’s structure and the ability to move. Bones form the framework and act as levers, while skeletal muscles attach to those bones and contract to produce movement when we choose to move. The other statements describe parts or controls that aren’t the defining components of this system: involuntary muscles belong to other systems (they’re not the main movers here), the nervous system’s control is about regulation rather than physical parts, and connective tissue supports the skeleton but isn’t the primary duo that enables movement.