Question

which component is represented by the letter x in the diagram?
heat
water
hydrogen
oxygen

Explanation:

Cellular respiration produces different products depending on oxygen availability. When oxygen is present, aerobic respiration occurs, producing carbon - dioxide, water and a large amount of ATP (36 ATP). When oxygen is absent, anaerobic respiration (fermentation) occurs, producing lactic acid and a small amount of ATP (2 ATP).

Answer:

Oxygen