7701. I was shocked at his crass behaviour.

✅ The correct answer is option C.
Indifferent : having no particular interest or sympathy; unconcerned.

Rigid : unable to bend or be forced out of shape; not flexible.

Stupid : having or showing a great lack of intelligence or common sense.

Difficult : needing much effort or skill to accomplish, deal with, or understand.

Crass : showing no intelligence or sensitivity.

Synonym of Crass is Stupid