Which metabolite is common in the respiratory breakdown of fats,carbohydrates,and proteins?

Which of the following biomolecules is common to respiration-mediated breakdown of fats,carbohydrates,and proteins?

Given below are two statements:
Statement $I$ - Reactions involved in Krebs cycle are anabolic and catabolic.
Statement $II$ - During oxidation of acetyl $CoA$,stepwise oxidation of the acetyl part of acetyl $CoA$ occurs.
In light of the above statements,choose the most appropriate answer from the options given below.

The breakdown of respiratory substrates is a $..........$ process.

Which of the metabolites is common to respiration mediated breakdown of fats,carbohydrates and proteins?