During transition from rest to steady-state exercise, ATP demands must be met initially by the ATP-PC system and anaerobic glycolysis since oxygen delivery to the cells cannot instantaneously increase. This lag in oxygen delivery is called:.
a. oxygen debt
b. oxygen deficit
c. EPOC
d. oxygen repayment

b. oxygen deficit

Explanation:

The energy provided during this deficit phase of exercise is used up to a steady state (or steady-rate) of oxygen consumption

so there by indicating that the mitochondrial respiratory major energy system is being used  

so correct option is oxygen deficit

I can't see option dear

Explanation: