FAD is reduced to get FADH₂ in a step of the Krebs cycle, which involves the conversion of:

Explanation

In the Krebs cycle, FAD is reduced to FADH₂ during the conversion of succinate to fumarate, a reaction catalyzed by the enzyme succinate dehydrogenase. This is the only step in the Krebs cycle where FAD is used as an electron acceptor. The other options involve different reactions: the conversion of malate to oxaloacetate involves NAD+ reduction, fumarate to malate involves hydration, and α-ketoglutarate to succinate involves NAD+ reduction.