Which of the Following Statements About Fast-Twitch and Slow-Twitch Fibers

Which of the following statements about fast-twitch and slow-twitch fibers is false?

A) In skeletal muscle, the most important factor determining the proportion of fast- and slow-twitch fibers is genetic heritage.
B) Aerobic training increases the oxidative capacity of intermediate fibers.
C) A single muscle may contain fast- and slow-twitch fibers.
D) Fast-twitch fibers fatigue slowly.
E) All of the above are true; none is false.