Genetics, age, body composition and what all influence an individual's level of flexibility.

The answer is: Level of physical activity

In general, people who are physically active tend to have higher level of flexibility compared to people who lead a sedentary life style. This happen because as you become more physically active, your body is got used to and develop the ability to do wider range of motion.

the cdc / centers for disease control and prevention

explanation:

d would be your answer