Final answer:
The correct example of an idiom is the phrase "raining cats and dogs" which means raining heavily.
Step-by-step explanation:
The correct example of an idiom is the phrase "raining cats and dogs" in the sentence "When I looked out the window, I saw it was raining cats and dogs." An idiom is a phrase or expression that has a figurative meaning different from its literal meaning. In this case, the idiom means that it was raining heavily.
Learn more about Idioms in English