Which Statement About Skeletal Muscle Is True

Multiple Choice

Which statement about skeletal muscle is true?

A) The fewer muscle fibers a motor neuron innervates, the larger the forces produced by a muscle.
B) A single action potential stimulates multiple twitches.
C) Twitches sum when action potentials arrive well separated in time.
D) The number of motor units activated and the frequency with which the motor units fire determine the level of tension in a muscle.
E) Summing of twitches occurs because ATP pumps in the sarcoplasmic reticulum are unable to clear ATP from the sarcoplasm between action potentials.