Read the sentence.
Afraid his mom would fly off the handle, Curran chose not to tell her about the dent in the car.
This sentence illustrates which of these?
idiom
colloquialism
slang
jargon
It's an Idiom because the mother is not going to "literally" fly off the handle, it is only a figure of speech and an idiom is a phrase or expression that typically presents a figurative non-literal meaning.
