The correct option is A Ubiquinone
Ubiquinone is a lipid-soluble benzoquinone and serves as an electron carrier in membrane-associated electron-transfer chains. Reduction of ubiquinone with one electron forms the semiquinone radical while with two electrons form ubiquinol. Being small and hydrophobic, it is freely diffusible within the lipid bilayer of the inner mitochondrial membrane. Due to its ability to carry both electrons and protons, it couples electron flow to proton movement. Acetyl CoA is the product of oxidative decarboxylation of pyruvate and enters Kreb cycle for complete decarboxylation. Condensation of Acetyl CoA with OAA forms citrate, the first tricarboxylic acid of Kreb cycle. Ferricyanide is the nonbiological electron acceptor. Thus, the correct answer is option A.