Final answer:
The idiom in the answer choices is "raining cats and dogs."
Step-by-step explanation:
An idiom is a phrase or expression that has a meaning different from the literal meaning of its individual words. In the given answer choices, the idiom is "raining cats and dogs." This idiom is used to describe a heavy or intense rain. It is not meant to be taken literally, but instead, it conveys the idea of rain falling heavily.
Learn more about Idioms in English