Why Should It Not Be Surprising That for Many Cells

Multiple Choice

Why should it not be surprising that for many cells water requires a protein for its transport across a membrane?

A) Water is very polar which inhibits its free diffusion across the membrane.
B) All molecules require transport proteins to cross a membrane.
C) The transport protein is needed to prevent the hydrolysis of the phospholipid chains as water crosses the membrane.
D) There is never a concentration gradient for water across the membrane to drive its transport.