An author is most likely to employ comic relief when there is great tension in the protagonist's situation. He will try to make the situation not so serious by employing some sort of comic relief.
The correct answer is When there is a great tension in the protagonist's situation.
To help the readers breathe for a while in the story, the author could employ a comic relief. This way, the readers will not be burdened with the great tension that is happening with the protagonist.
