When atrophy occurs, what happens to the muscle?

Atrophy describes the process where muscle fibers decrease in size and strength due to a variety of factors, such as disuse, aging, or certain medical conditions. When muscle tissue is not actively used or is subjected to a lower level of stress than it's accustomed to, the body begins to break down the muscle proteins, leading to a reduction in muscle mass. This can result in weaker muscles and a decrease in physical function. Consequently, option D accurately reflects that when atrophy occurs, the muscle decreases in size, which is the main consequence of this physiological process.