This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Metabolism of protein and amino acid, Subject name: Biochemistry
At which level does methionine enter the TCA cycle? 
Select and explain. 
A. Acetyl co A, B. Succinyl co A, C. Oxaloacetate, D. Pyruvate
B: Succinyl co A
Answer: B: Succinyl co A 
Explanation: Reference: Lehninger illustrated biochemistry 5th edition