问题
单项选择题
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
参考答案：D
解析：
本题考察虚拟语气。but for起到了对过去虚拟的条件旬作用，后面自然要选would/could/might/should+have done结构了。