From the processes given, we can discard photosynthesis because it creates food molecules, it doesn't break them to obtain ATP.
We can also discard the electron transport chain because it doesn't use food molecules, although it produces ATP.
Cellular respiration refers to glycolysis, the Krebs cycle, and the electron transport chain, and it involves oxygen molecules, so is not the right answer.
Fermentation occurs in the absence of oxygen and makes energy from carbohydrates, so that would be the right answer (option B)
