You’d better not call Mr Green between 7 and 8 this evening，for he ________ an important talk then.[ ]

The family have _______ in Yancheng for a week.

n’t surf the internet before youfinish your homework, ______ you

Did you meet with the famous space hero,Yang Liwei—_____ I had come here earlier.

So although Fleming discovered penicillin, it was over a decade ___________someone else turned penicillin into the great drug of the 20th century