In Chemiosmosis, the Most Direct Source of Energy Used to Convert

In chemiosmosis, the most direct source of energy used to convert ADP + i to ATP is energy released ________.

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