Which statement is true?

A.   A fit person’s heart may work more efficiently than a nonfit person’s heart because genetics determines the heart’s efficiency.

B.    A fit person’s heart may work the same as a nonfit person’s heart because genetics determines the heart’s efficiency.

C.   A fit person’s heart works more efficiently by pumping less blood with more beats.

D. A fit person’s heart works more efficiently by pumping more blood with fewer beats.