have no idea

Từ điển Oxford Advanced Learner 8th

have no iˈdea | not have the faintest, first, etc. idea idiom
(informal)used to emphasize that you do not know sth
•‘What's she talking about?’ ‘I've no idea.’
•He hasn't the faintest idea how to manage people.
•I had no idea she'd had such a difficult life.
•I don't have any idea where he is.
Main entry: ↑idea_idiom