Atractyloside Is a Poison That Inhibits the Transport of ADP

Atractyloside is a poison that inhibits the transport of ADP from the cytosol across the mitochondrial membranes and into the mitochondrial matrix. The direct effect of this drug is to stop ATP synthesis because:

A) ADP is a necessary substrate for the reaction catalyzed by ATP synthase.
B) it prevents proton pumping across the inner mitochondrial membrane.
C) it prevents electron transfer to O₂.
D) it prevents electron transfer from NADH to complex I.