In the following question, out of the given four alternatives, select the alternative which best expresses the meaning of the Idiom/Phrase.
Once in a blue moon

Correct option is C

The correct meaning of the idiom "Once in a blue moon" is Very rarely.
Explanation: The phrase "Once in a blue moon" is used to describe an event that happens infrequently or only on rare occasions.
Example: She goes on vacation once in a blue moon because of her busy work schedule.