Question

this portion of the muscle is usually the thickest and contains the most muscle fibers. myofibril muscle belly tendon endomysium

Explanation:

The muscle belly is the thick - est part of a muscle and contains the most muscle fibers. Myofibrils are components within muscle cells, tendons attach muscle to bone, and endomysium is connective tissue around individual muscle fibers.

Answer:

Muscle belly