The correct option is A Krebs Cycle
Krebs’ cycle starts with condensation of acetyl group (acetyl CoA) with oxaloacetate (4-carbon compound) in the presence of a condensing enzyme citrate synthase to form a tricarboxylic, 6-carbon compound called citric acid. It is the 1st product of Krebs cycle. CoA is liberated. Krebs cycle is also named as citric acid cycle (CAC) or tricarboxylic acid (TCA) cycle after the initial condensation product i.e., citrate or citric acid.
Glycolysis is the process of partial oxidation of glucose or similar hexose sugar into 2 molecules of pyruvic acid through a series of ten enzyme mediated reactions releasing some energy (as ATP) and reducing power (as NADH).
Calvin cycle is another name for the C3 cycle of Dark reaction of photosynthesis.