Which of the Following Statements Are True of External Respiration

Multiple Choice

Which of the following statements are true of external respiration and internal respiration? (Read carefully and select all of the correct statements.)

A) The P in PO₂ means presence of oxygen.
B) In the alveoli, PCO₂ is low and PO₂ is high.
C) In the tissues, PO₂ is high and PCO₂ is low.
D) Internal respiration takes place in the pulmonary capillaries.
E) External respiration takes place in the nasal cavities as the air is warmed
F) The pressure gradient of a gas is much the same as a concentration gradient.