Answer: The correct answer is-
Mitochondrial matrix.
Aerobic respiration is a metabolic process in which food ( such as glucose) is oxidized to produce a large amount of energy in the form of ATP ( adenosine triphosphate) that can be used for various cellular activities. Carbon dioxide and water are released as byproducts in this process.
This process takes place in three steps that are- Glycolysis ( occurs in cytoplasm) , Kreb cycle (occurs in the matrix of mitochondria), and electron trasport chain ( in the inner mitochondrial membrane).
During Kreb cycle, Acetyl Coenzyme- A (formed by decarboxylation of pyruvate, which is end product of glycolysis) is oxidized through a series of enzymatically derived reactions so as to obtain ATP, NADH and FADH₂.
NADH and FADH₂ are electron carriers that are further used in the next stage ( electron transport chain) to derive large amount of energy in the form of ATP.