How does heredity affect flexibility?

a.
heredity does not affect flexibility.
b.
heredity affects which joint types a person develops.
c.
heredity affects the amount of flexibility present in joints.
d.
heredity affects how joint structure is developed.

I believe the answer is: D. Heredity affects how joint structure is developed

Some people are genetically gifted to develop a joint structure which allow them to rotate their joint in further extent compared to normal people.

These people tend to have higher flexibility and would be constantly scouted for olympic teams, especially for gymnastics type sports