Which Oxidation Reaction Requires the Coenzyme FAD Because It Involves $\alpha$

Which oxidation reaction requires the coenzyme FAD because it involves oxidation of a carbon-carbon single bond to a double bond?

A) oxidation of isocitrate to $\alpha$ -ketoglutarate
B) oxidation of $\alpha$ -ketoglutarate to succinyl-CoA
C) oxidation of succinate to fumarate
D) oxidation of malate to oxaloacetate
E) oxidation of pyruvate to acetyl-CoA