Jargon because he/she is using special words or expressions and it is quite hard to understand to others.
Example: She was on cloud 9 after the results were declared.
Hope it helped!
This expression is a form of slang. This is because jargon is usually a style of language used within a specific group of people and that uses terms that can only be understood by that set of people and that makes no sense unless you have the context. It is not general English either as the terms used are not common in the English learned outside of native-speaking countries. An idiom is basically a composed word that generates from another two but that you cannot derive its meaning from the two individual composing words. It has a meaning all on its own. But this expression has none of the previous options carachteristics. It is rather a phrase that uses very informal vocabulary like gnarly and flip to give meaning to an idea and even underline the expression of one speaker to the other. Correct answer then in C.
