In Chemiosmosis, What Is the Most Direct Source of Energy

Multiple Choice

In chemiosmosis, what is the most direct source of energy that is used to convert ADP + i to ATP?

A) energy released as electrons flow through the electron transport chain
B) energy released from substrate-level phosphorylation
C) energy released from movement of protons through ATP synthase, down their electrochemical gradient
D) energy released as electrons are transported across the inner mitochondrial membrane