Select the most appropriate meaning of the given idiom.
A fly on the wall

Correct option is B

Option (b) is the correct meaning of the given idiom.
Idiom: A fly on the wall — someone who observes a situation without being noticed. (चुपचाप निरीक्षण करने वाला)
Example: I would love to be a fly on the wall during their board meetings.
Other related idioms:
· Behind closed doors – in private.
· See through someone – to understand the true nature of someone.
· Keep an eye on – to watch someone/something closely.