Marathon runners: A. are always very thin.
B. only eat carbohydrates.
C. tend to have more slow-twitch muscle fibers,
D. can run only one or two marathons a year.

c

Explanation:

marathon runners tend to have more slow-twitch muscle fibers, while sprinters will have more fast-twitch muscle fibers which allow faster movment but does not last as long while marathon runners have more paced and can last a long time.

C.tend to have more slow twitch-muscle fibers

Explanation:

muscle fibers are focused on smaller movements, posture control, and fatigue resistance all of witch contribute to marathon runners.

answer; ///i believe that the correct answer is(5)

take a break move to stretching and slowly work back into physically exercising if the problem continues go to a doctor or physical therapist