You promised your friend a letter; you ought to ______ days ago.
| A．write | B．be writing | C．have written | D．be written |
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 |
_________ she would have avoided the accident.
| A．She was more careful | B．If she was more careful |
| C．Had she been more careful | D．She had been more careful |
Seldom _________ any mistakes during my past five years of teaching in this university.
| A．would I make | B．I did make |
| C．should I make | D．did I make |