The correct answer is D.
Acetyl CoA is condensed with a four carbon intermediate , oxaloacetate, to form citrate. The citrate then goes through a series of chemical transformations , losing two carboxyl groups as CO2.
The Krebs cycle serves two main purposes namely.
1. to increase the cell's ATP producing potential by generating reduced electron carriers such as NADH and reduced ubiquinone.
2. to provide the cell with a variety of metabolic precursors which are one FADH and four NADH molecules