Physical fitness components are divided into two categories: health-related (cardiovascular endurance, muscular strength, muscular endurance, flexibility, body composition) and skill-related (agility, balance, coordination, speed, reaction time, power). The question asks specifically for a skill-related component linked to quickly changing direction.
Agility is defined as the ability to change the position and direction of the body quickly and effectively while maintaining control. In basketball, players must constantly cut, pivot, and change direction to evade defenders, drive to the basket, or stay with an opponent on defence. This makes agility the most directly relevant component.
Speed refers to how fast a person can move from one point to another in a straight line. Reaction time is the interval between a stimulus and the initiation of a response. Power is the ability to exert maximum force in the shortest time. While all of these matter in basketball, none of them specifically describes the ability to change direction rapidly, which is the defining feature of agility.