This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Biochemistry
Which of these is a conservative mutator: 
Select and explain. 
A. Glutamic acid- glutamine, B. Histidine-glycine, C. Alanine- leucine, D. Arginine-aspaic acid
C: Alanine- leucine
Answer: C: Alanine- leucine 
Explanation: C i.e. Alanine - leucine