The Proportion of Fast- and Slow-Twitch Fibers Found in an Individual's

Multiple Choice

 The proportion of fast- and slow-twitch fibers found in an individual's quadriceps muscle is primarily determined by the

A) individual's diet.
B) number of hours the individual spends each week engaged in anaerobic activity, like weightlifting.
C) the type of ACTN3 genes that person has.
D) number of hours the individual spends each week engaged in aerobic activity, like running or cycling.