Answer:
The correct answer is a. electron transport.
Step-by-step explanation:
Cytochromes play an important role in the transfer of electrons from NADH and FADH2 to molecular oxygen during oxidative phosphorylation in mitochondria. So cytochromes makes the electron transport chain of mitochondria.
Therefore if cytochrome b enzyme becomes defective then cytochrome b will not work and the transport of electron through electron transport chain will stop. So there will not be any production of ATP in oxidative phosphorylation due to the blockage in electron transport.
Therefore the right answer is a. electron transport.