The correct option is D Succinate dehydrogenase
Krebs cycle is a series of chemical reactions that occurs inside the mitochondria of aerobic organisms that aims at releasing the stored energy of organic food substances through the stepwise oxidation of acetyl CoA obtained from pyruvate during glycolysis. It is also known as TCA or tricarboxylic acid cycle or citric acid cycle (CAC) after the name of its initial product that is formed i.e citric acid or citrate.
In the 6th step of Krebs cycle, oxidation of succinate occurs. Succinate undergoes dehydrogenation (removal of hydrogen) to form fumarate with the help of a membrane based enzyme succinate dehydrogenase. All enzymes of the TCA cycle are located in the mitochondrial matrix except succinate dehydrogenase which is located in the inner mitochondrial membrane in eukaryotes and the cytosol in prokaryotes.