Correct Answer: Whisper

Solution : The correct answer is the third option.

Whisper , which means to speak softly or quietly, often in a secretive manner, is the opposite of yell, which means to shout in a loud, sharp way.

The meanings of the other options are as follows:

Notify : To inform or alert someone about something.

Indemnify : To compensate or protect someone against potential losses.

Terrorize : To instil fear or intimidate someone through violent actions.

Therefore, the antonym of yell is whisper.