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
网友回答
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。