Which of the following is the order of pCO2 from low to high?

Which of the following is the order of pCO2 from low to high?
A.Exhalation ＜ tissue cell ＜ venous blood ＜ alveolar gas
B.exhalation ＜ alveolar gas ＜ venous blood ＜ tissue cell
C.exhalation ＜ alveolar gas ＜ tissue cell ＜ venous blood
D.venous blood ＜ exhalation ＜ alveolar gas ＜ tissue cell
正确答案：exhalation ＜ alveolar gas ＜ venous blood ＜ tissue cell