Q. Which of the following statement about the structure of skeletal muscle is true ?

A) The light bands of the sarcoma are the region where actin and myosin filaments overlap
B) When the muscle contracts, the A bands of the sarcomere lengthen
C) When the muscle contracts, the H zone of the sarcomere shortens
D) The sacoplasm of the muscle cell is contained within the sarcoplasmic reticulum

... Answer is C).When the muscle contracts, the H zone of the sarcomere shortens

According to the sliding filament theory of muscle contraction, individually linked sarcomeres shorten (contract), a condition that results when the filaments slide past each other. The movement of the actin filaments towards the middle of the sarcomere occurs as the myosin cross-bridges attach themselves to the actin sites. Muscle contraction (shortening) is reflected in the sarcomere as a decrease in the I band as the Z lines (which are located at the ends of the actin filaments) move closer together. The width of the A band (the myosin filament) remains unchanged.