To increase the effectiveness of exchange surfaces lining the lungs and the intestines, evolutionary pressures have
A) increased the exchange surface area with folds and branches.
B) increased the thickness of the membranes in these linings.
C) increased the number of cell layers in these linings.
D) decreased the metabolic rate of the cells in these linings.
E) increased the volume of the cells in these linings.
Answer: A