The idiom "Red letter day" means:
Aa bad day
Ba memorable day
Ca holy day
Da sad day
Aa bad day
Ba memorable day
Ca holy day
Da sad day
Related Questions:
He has a habit of ‘building castles in the air’ (Choose the word nearest in meaning of the underlined words)
He is regarded as Manager’s 'right hand man'. (Choose the alternative which best expresses the meaning of the idiom/phrase underlined)