In which sentence is the punctuation correct?
A) I don't understand why he left
B) I don't understand, why he left
C) I don't understand why, he left
A) I don't understand why he left
Below is an instruction that describes a task. Write a response that appropriately completes the request.

### Instruction:
In which sentence is the punctuation correct?

### Response:
A) I don't understand why he left