To warm up before a run, David begins by completing quad and hurdler's stretches. Choose the answer that accurately evaluates his choice of warm-up activities.
a) These activities are appropriate because they prepare muscles for intense movement.

b) These activities are not appropriate because the muscles stretched are not warm yet.

c) These activities are appropriate because they make the leg muscles more flexible.

d) These activities are not appropriate because they stretch muscles not used in the exercise.