Identify the site of oxidative phosphorylation.

Given below are two statements.
$Statement-I$: During aerobic respiration, $ETS$ releases energy in a stepwise manner to prevent damage to cells.
$Statement-II$: During aerobic respiration, $ETS$ provides water molecules.
In the light of the above statements, choose the correct answer from the options given below.

Electron transport system occurs in $:-$

Oxygen is critical for aerobic respiration. Explain its role with respect to $ETS$.

$O_2$ maintains the operation of the Krebs cycle by:

In the $ETS$ (Electron Transport System),how many molecules of each cytochrome are required for the transfer of $2$ $e^-$?