Okay so the question on my biology homework goes like this:

Which of the following steps best illustrates how the cell extracts energy from glucose?

a) Electrons move along the ETC spontaneously
b) phosphates are added to glucose during glycolysis to make glucose unstable
c) water us formed after O2 accepts electrons and a proton
d) FAD takes electrons from succinate in the Citric Acid Cycle to become FADH2
e) Protons flow through ATP synthase by moving from a high to low concentration

Please help me out it's the last question and I don't want to get it wrong.