--- You seem to be familiar with London.
--- I ______ there for three years. It’s great to be back.
| A.lived | B.had lived | C.have lived | D.live | 
Factory workers have to work very hard, and _________.
| A.farmers do so | B.farmers work so | 
| C.so have farmers | D.so do farmers | 
Only when David did it a second time _________.
| A.he realized his mistake | 
| B.he was realizing his mistake | 
| C.did he realize his mistake | 
| D.he did realize his mistake | 
So instructive _________ that the student wanted to see it again. 
 A. was the film B. it was the film
 C, the film was D. the film it was
Not until I went to America _________ what kind of country it was.
| A.did I know | B.I did know | 
| C.I didn't know | D.I could know | 
_________ forget my hometown and my happy childhood.
| A.Never I will | B.Never will 1 | 
| C.Never I | D.I never have |