Once in a……moon

Can you complete this famous English idiom?

Once in a…….. moon.

a) red

b) green

c) blue

The answer is below! ↓

 

 

Once in a blue moon. It means “very rarely”.

Here is an example.

Nina: How often do you go to the cinema?

Ted: I go once in a blue moon. I’m so busy with my business, I have hardly any free time!