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:考查虚拟语气。根据But for their help要不是他们的帮助;可知这是一个与过去事实相反的含蓄的虚拟语气句,后面主句应该使用情态动词+have done;句意:要不是他们的帮助,我们不能够及时完成这项计划。