The correct option is A Cytoplasm
Cytoplasm
Aerobic respiration requires oxygen, but during strenuous exercises, such as sprinting, oxygen is used up faster than it can be delivered to the muscle cells. Instead, ATP is produced anaerobically, with pyruvate being used as an oxidant instead of oxygen. Pyruvate itself is converted to lactic acid in the cytoplasm. This is a less efficient way producing energy but can occur much more quickly.