In China, almost all gammar books say the tag question of 'He must have arrived' is 'hasn't he' and that of 'He must have arrived yesterday' is 'didn't he'. And they say 'mustn't he' is wrongly used.
So I asked the question here. I searched the BNC and found in British English you use 'mustn't' and in American English you use 'didn't/hasn't'.
I doubt that those grammar books written by Chinese writers are holding a one-sided view.
I'm hoping both American and British native English speakers can talk about this and help me. Thanks a lot.
Last edited by joham; 07-Mar-2009 at 06:47.