Question

At sea level, the partial pressure of oxygen in the lungs is 100 mmHg and that in blood in pulmonary capillaries is 40 mmHg. The pressure gradient across the respiratory membrane will be

A. 40 mm Hg
B. 50 mm Hg
C. 60 mm Hg
D. 80 mm Hg
E. 90 mm Hg