Cells A and B are the same size, shape, and temperature, but cell A is metabolically less active than cell B; cell B is actively converting oxygen to water in cellular respiration. Oxygen will diffuse more rapidly into cell because .

A. A; its membrane transport proteins will not be saturated
B. A; the concentration gradient there is shallower
C. B; the diffusion gradient in cell B is steeper
D. B; the oxygen molecules inside cell B have a higher kinetic energy
E. B; the gradient of oxygen is oriented in the opposite direction compared to cell A