Athletes warm up to ensure their joints are flexible. flexible joints
a. important to prevent athletic injury.
b. naturally occurring as you move further into your fitness program.
c. important so you can run faster or reach farther.
d. only a concern for cross-training athletes.

Flexible joints are A. important to prevent athletic injury. It is quite important to stretch and warm up before exercising so as not to hurt yourself and your body and muscles. Flexibility is relevant for everyone, not just cross-training athletes. It doesn't occur naturally, you have to train to get there. It is important for everything, not just running.