"Once in a blue moon" is an idiom, meaning something that happens very rarely.
An idiom is a phrase with a meaning different from the literal interpretation of its words.
The idiom "as different as night and day" means two things are completely opposite.
Although we are brothers, but we are as different as day and night.
The idiom “Lend an ear” means توجہ دینا
"To smell a rat" means to sense that something is wrong or suspicious.
It originates from the idea of detecting hidden danger, like a rat in hiding.
If someone is burning the midnight oil, they are staying up very late in order to study or do some other work.
Here all the other idioms are incorrect.
"Beat around the bush" is an idiom meaning to avoid saying something directly or not addressing the main point.
It is used when someone is being indirect or evasive.
The idiom "odds and ends" refers to miscellaneous small items or remnants.
It often leftover or scattered pieces with little individual importance.
Like a sitting duck means ignorant.
Like a sitting duck means وہ شخص جو بآسانی زد میں آسکے
The idiom "on the ball" means being quick to understand and react to things.
In this sentence, it refers to someone giving a sharp and accurate assessment.
The idiom "flogging a dead horse" means trying to continue with something that has no hope of success.
In this context, it suggests further appeals are pointless and a waste of time.