Firstly, try to remember what the intermediate reaction was called (Link Reaction). Name this, as if the name was not stated in the first place in the question, the examiner is most likely looking for your knowledge of its existence. Next, break down what is involved in the Link Reaction: 1st action - Pyruvate enters from cytoplasm to mitochondria matrix. 2nd Action - Pyruvate is dehydrogenated to release H, accepted by NAD to form NADH, 3rd Action - Molecule of CO2 is removed. This produces a 2C acetate group, combining with Acetyl Coenzyme A, which then enters the krebs cycle. Each action, and naming the whole reaction, could potentially score 1 mark.