Answer:
Mitochondria
Step-by-step explanation:
Mitochondria are organelles found in essentially all eukaryotic cells. They are the sites the later stages of aerobic respiration - which is the process that produces the vast majority of the ATP in the cell. Aerobic respiration requires oxygen to convert sugar into energy, releasing carbon dioxide and water as by-products.
The first stage of aerobic respiration - glycolysis - occurs in the cytoplasm. However, the next two stages - Krebs cycle and the electron transport chain -occur in the mitochondria. These stages are the main producers of ATP in the cell.