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

Fats are broken into fatty acids and glycerol; fatty acids enter the pathway as Acetyl CoA. Proteins are broken into amino acids, some of which enter as pyruvate or Acetyl CoA. Carbohydrates enter as glucose and eventually form Acetyl CoA before entering the Krebs cycle. It is the common entry point.