Answer:
C) I did not realize how much my vacation would affect my work hours. I might need 1–2 extra days to complete everything.
Explanation:
The most ethical answer is option C because it is explaining the real reasons why he is not going to meet the deadline, the other options are not telling the truth, and if he sends any of them, he is being dishonest and making a bad reputation for himself. Telling the truth is the most ethical answer that he can give.