—Have you seen Maragaret? The boss is looking for her everywhere.—She________the train, otherwise she would have arrived here by now.

I think that's unlikely to happen, but if that ______ occur, both America's and China's interest would be severely damaged.

 I’m really tired of Tom because he ______ keep asking silly questions. 

–Must I return the story book tomorrow, madam?       –No, you ______ bring it here next Monday.

Last night Li Ping watched the football match at my home, so he________ in his office.