Which Statement About Human Breathing Is True

Which statement about human breathing is true?

A) It involves countercurrent gas exchange.
B) With maximum inhalation,a person can breathe in as much air as the lungs can hold.
C) A residual volume of air remains in the lungs even with maximum exhalation.
D) There is a long diffusion path between the blood and the air (greater than 0.5 mm) .
E) The partial pressure of O₂ within the alveoli is the same as that of the external air.