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 - this sentence has correct punctuation.
Complete the following task based on the instruction and optional input provided.### Instruction:
In which sentence is the punctuation correct?

### Input:
A) I don't understand why he left
B) I don't understand, why he left
C) I don't understand why, he left

### Output:
A) I don't understand why he left - this sentence has correct punctuation.