The correct option is D Krebs' cycle
The pyruvic acid formed during glycolysis is oxidised to CO2 and H2O in a cycle called Krebs' cycle. It was named after the scientist Hans Krebs who first elucidated it in flight muscles of pigeon. In these reactions, hydrogen atoms are removed from the acetyl CoA and transferred to the coenzyme for further processing in the electron transport system. The cycle is also called Citric Acid cycle (CAC, because of the formation of citric acid in the first step of this cycle) or TCA cycle (because many intermediate compounds formed in the cycle have three carboxyl groups). The reactions of the Krebs cycle require the presence of oxygen and are confined to mitochondrial matrix. This cycle serves as a common oxidative pathway for carbohydrates, fats and proteins.