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
Base substitution of GAC (Asp) to GAG (Glu) is an example of: 
Select and explain. 
A. Point mutation, B. Silent mutation, C. Non-sense mutation, D. None
A: Point mutation
Answer: A: Point mutation 
Explanation: A i.e. Point mutation