Which of the following is a component of physical fitness?

Cardiovascular endurance is a fundamental component of physical fitness that reflects the body's ability to take in, transport, and utilize oxygen during sustained physical activity. This capability is essential for overall health, performance, and the ability to engage in prolonged exercise without excessive fatigue. Improving cardiovascular endurance can enhance the efficiency of the heart and lungs, leading to better stamina and physical capability in various activities.

While other options such as muscular flexibility and agility are also important aspects of a comprehensive fitness program, they do not encompass the same critical role in endurance performance and overall health that cardiovascular endurance does. Body mass index, on the other hand, is a measurement used to assess body weight in relation to height and does not directly measure physical fitness itself.