Larger Single-Celled Organisms Require a Higher Oxygen Concentration Than Smaller

Larger single-celled organisms require a higher oxygen concentration than smaller ones do because the large cells

A) have a faster metabolic rate per unit mass.
B) have a slower metabolic rate per unit mass.
C) have a lower surface area-to-volume ratio.
D) have a greater surface area-to-volume ratio.
E) divide more quickly than small cells do.