To solve this problem, we need to analyze each statement to identify the incorrect one:$\newline \bullet$Option 1: During aerobic respiration, role of oxygen is limited to the terminal stage.$\newline$ - Oxygen acts as the final electron acceptor in the electron transport chain (ETC), which is the terminal stage of aerobic respiration.$\newline$ - This statement is correct.$\newline \bullet$Option 2: In ETC, one molecule of NADH+H+ gives rise to 2 ATP molecules, and one FADH2 gives rise to 3 ATP molecules.$\newline$ - Typically, one NADH+H+ yields about 3 ATP molecules, and one FADH2 yields about 2 ATP molecules.$\newline$ - This statement is incorrect.$\newline \bullet$Option 3: ATP is synthesized through complex V.$\newline$ - Complex V, also known as ATP synthase, is responsible for the synthesis of ATP.$\newline$ - This statement is correct.$\newline \bullet$Option 4: Oxidation-reduction reactions produce proton gradient in respiration.$\newline$ - The electron transport chain involves a series of oxidation-reduction reactions that help establish a proton gradient across the inner mitochondrial membrane.$\newline$ - This statement is correct.$\newline$Therefore, the incorrect statement is Option 2.