The oxidation of one $NADH_2$ yields (in $ATP$)

The last electron acceptor in the Electron Transport System $(ETS)$ is

Given below are two statements.
Statement-$I$: During aerobic respiration,$ETS$ regenerates co-enzymes such as $NAD^+$ and $FAD^+$ from their reduced forms $NADH + H^+$ and $FADH_2$.
Statement-$II$: During aerobic respiration,$ETS$ generates a major amount of energy in the form of $ATP$ molecules.
In the light of the above statements,choose the correct answer from the options given below.

Explain $ETS$.

Cytochrome helps in

Aerobic respiration,which yields maximum $ATP$ molecules,is completed in: