Question

what does the idiom once in a blue moon mean?
a something that happens every day
b something that happens very rarely
c something that is always blue
d something that happens during the night

Explanation:

The idiom "once in a blue moon" is a common English idiom. Its meaning is related to the frequency of an event. A blue moon (the second full moon in a month) is a relatively rare astronomical event, so the idiom is used to describe something that occurs very infrequently. Option A is incorrect as it describes a daily event. Option C is incorrect as it misinterprets the idiom literally (about color) instead of figuratively. Option D is incorrect as the idiom has nothing to do with the time of day (night) but with rarity.

Answer:

B. Something that happens very rarely