The correct option is A Enzyme complex I accepts electrons and H+ from NADH and FADH2
Electron transport chain is responsible for oxidative phosphorylation in which e– and H+ of NADH are accepted by complex I and then the electrons move through different carriers. 6 protons are pumped in intermembranous space which later diffuse to the matrix through F0−F1 (ATP synthase) to form 3 ATP. FADH2 always enters in ETS through complex II. Cytochromes b–c1, c,and a–a3 are arranged in ETS according to the order of redox potential. Cytochrome c is a mobile electron carrier.