Hello,
The answer is option C "fat".
Reason:
The word fat would cause emotion to a person but a negative connotation is a word with two parts which causes feelings and emotions which could hurt someone and options A, B, and D dont hurt feelings because they are saying it in a kinda nice way therefore the answer should be option C.
If you need anymore help feel free to ask me!
Hope this helps!
~Nonportrit