Cellular respiration
Cellular respiration is a process by which the cell obtains energy in the form of ATP.
The process of obtaining energy can occur with oxygen (aerobic respiration) or in the absence of oxygen (fermentation). However, fermentation generates less energy than aerobic respiration and is therefore used only in cases of energy "emergency".
Oxygen is a very important factor in ATP synthesis. Therefore, it is considered a limiting factor. So option "C" is the answer.