How Is the Energy Used to Make ATP Via the Electron

How is the energy used to make ATP via the electron transport chain generated?

A) The energy from electrons bound to reduced coenzymes is used to create a steep electrochemical gradient.
B) Electrons bound to NADH are used to generate a H⁺ ion gradient across the inner mitochondrial membrane.
C) Electrons bound to FADH2 are used to generate a proton gradient across the inner mitochondrial membrane.
D) Electrons bound to NADH are used to generate a proton gradient across the inner mitochondrial membrane.
E) All of these are correct.