At What Exercise Level Would the Alveolar-Arterial PO₂ Difference Be

At what exercise level would the alveolar-arterial PO₂ difference be expected to change?

A) It will increase when 40% or more of maximum oxygen consumption is reached
B) It will increase when 60% or more of maximum oxygen consumption is reached
C) It will start to decrease when 40% or more of maximum oxygen consumption is reached
D) It will start to decrease when 60% or more of maximum oxygen consumption is reached