_________ development of nuclear weapons is _________ threat to mankind.
| A．The; a | B．The; the | C．A; a | D．A; the |
____no need for us to discuss the problem again since it has already been solved.
| A．It has | B．There has | C．We have | D．There is |
I didn't like aunt Lucy,who __________ without warning and bringing us presents.
| A．always turned up | B．has always turned up |
| C．had always turned up | D．was always turning up |
You'd better get all the work _________ before you leave.
| A．finishing | B．to finish | C．finished | D．be finished |
At midnight the enemy attacked _________.
| A．without warning | B．without notice | C．without permission | D．A or B |
He had to___ before they finished the course because they were not well disciplined.
| A．drop in | B．drop out | C．drop off | D．drop by |