Answer: The correct answer is -
B) NADH and FADH2.
NADH and FADH2 are electron carriers that provide electrons, which move across four protein complex (Complex I to complex IV) in the inner mitochondrial membrane.
These are high energy electrons and ultimately help in the generation of large amount of energy in the form of ATP.
The flow of electrons across protein complex leads to change in shape their shapes, due to which protons are pumped across the inner membrane ( that is from mitochondrial matrix to the intermembrane space).
As a result, a concentration gradient of Hydrogen ions is formed across the membrane.
By diffusion, the hydrogen ions travel back through a special channel called ATP sythase. This channel utilizes the energy of the flow of the Hydrogen ions to form ATP.
