The common intermediate of carbohydrate, protein and lipid metabolism is–

Correct option is C

Option (c): Correct
• Acetyl CoA is the central metabolic intermediate:
– Carbohydrates → Pyruvate → Acetyl CoA
– Fatty acids → β-oxidation → Acetyl CoA
– Amino acids → deamination → Acetyl CoA
• It enters the TCA cycle, linking all major nutrient pathways.
Option (b): Incorrect
• Pyruvic acid connects carbohydrate and amino acid metabolism but not lipids directly.
Option (a): Incorrect
• Ammonia is a protein metabolism by-product only.
Option (d): Incorrect
• Phosphoglyceraldehyde is a glycolysis intermediate, not common to all three pathways.