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.
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.
