The factor(s) that determine the duration of a twitch in various types of fibers is the speed of the

A. removal of Ca2+ ions from the sarcoplasm only.

B. hydrolysis of ATP only.

C. movement of Na+ across their membranes only.

D. removal of Ca2+ ions from the sarcoplasm and hydrolysis of ATP.

E. removal of Ca2+ ions from the sarcoplasm and hydrolysis of ATP and movement of Na+ across their membranes.