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.
