Explanation should include

the principles of static stretching, ballistic stretching, and proprioceptive neuromuscular facilitation (PNF)
considerations of intensity, duration, and frequency
the differences between elastic and plastic deformation
the concept that flexibility is important because it increases joint range of motion, facilitates reflex inhibition, and enhances the performance of the activities of daily living.

Process/Skill Questions:

What is static stretching? How is it performed? Why is it important?
What is ballistic stretching? How is it performed? Why is it important?
What is PNF stretching? How does PNF take advantage of muscular contraction and relaxation? Of agonist and antagonist relationships? Why is PNF stretching important?
What is the difference between flexibility and range of motion?
What is dynamic stretching? When is it more appropriate than static stretching?