Which of the Following Is Not a Reason for Erythrocytes

Multiple Choice

Which of the following is not a reason for erythrocytes' flattened "doughnut" shape

A) It increases the surface area available for gas diffusion.
B) It allows them to fit together with leukocytes to facilitate the transport of both.
C) It allows them to "stack" together to pass through small blood vessels more efficiently.
D) It gives them flexibility so that they can pass through the circulation more easily.
E) It allows the minimum distance for diffusion of gases.