Which of the following best describes flexibility?

Flexibility is best described as the capacity of a muscle to stretch and lengthen, which directly relates to how pliable muscles are and how easily they can move through their full range of motion. This is an essential aspect of physical fitness, as it allows for better performance in various activities and helps prevent injuries by accommodating the demands placed on the musculoskeletal system. Flexibility is influenced by factors like muscle elasticity, joint structure, and connective tissue properties, which enable muscles to move fluidly and adapt to different movements.

The other options highlight different concepts related to physical abilities. The first option pertains to strength, which is about exerting force. The third option focuses on overall strength and endurance, emphasizing the ability to withstand pressure. The fourth option deals with joint function but does not specifically address the muscle's ability to stretch. Therefore, the best choice regarding flexibility specifically targets the muscle's capacity to stretch and lengthen.