An idiom is a phrase used to represent something that has nothing to do with it and is not literal. For example: raining cats and dogs means it's raining hard and not literally raining animals. Seething with rage is not an idiom as seethe basically means mad or angry. Angry or mad with rage can be literal and is not an idiom.
This was very tough between b and c but im gonna have to say its b because its more literal than c is
