This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Classification and metabolism of amino acids, Subject name: Biochemistry
Which of the following amino acid can produce oxaloacetate directly in a single reaction? 
Select and explain. 
A. Alanine, B. Cysteine, C. Threonine, D. Aspaate
D: Aspaate
Answer: D: Aspaate 
Explanation: Alanine, Cysteine and Threonine can also produce oxaloacetate but pyruvate only. Aspaate can directly produce oxaloacetate in a single step, i.e. transamination reaction.