问题补充:
But for their help,we the program in time.
A. can not finish
B. will not finish
C. had not finished
D. could not have finished
答案:
A. can not finish
B. will not finish
C. had not finished
(答案→)D. could not have finished
解析:本题考察虚拟语气.But for起到了对过去虚拟的条件句作用,后面自然要选would/could/might/should+have done结构了.