Assertion (A): Aerobic process of respiration takes place only in the presence of oxygen.

Reason(R):  Role of oxygen is limited to the terminal stage of ETS.

Both (A) and (R) are true and (R) is not the correct explanation of (A)

Assertion (A) is true. Aerobic respiration is a type of cellular respiration that requires the presence of oxygen (O₂) as the final electron acceptor in the electron transport chain (ETC). In the presence of oxygen, glucose and other fuel molecules undergo complete oxidation, yielding carbon dioxide (CO₂) and water (H₂O) as end products. The complete breakdown of glucose to CO₂ and H₂O in the presence of oxygen results in the highest ATP yield during cellular respiration.

Reason (R) is also true. In the electron transport chain (ETC), oxygen's role is confined to the final stage, where it acts as the terminal electron acceptor. During oxidative phosphorylation, electrons derived from NADH and FADH₂ are transferred through a series of protein complexes in the inner mitochondrial membrane. Oxygen accepts these electrons at Complex IV (Cytochrome c Oxidase) and combines with protons (H⁺) to form water (H₂O).