问题
选择题
The emergency required that all the tasks _____ at least two days ahead of time．
A．to complete B．should complete C．be completed Dshould have been completed
答案
答案：C
考查虚拟语气。句意：紧急需要要求所有任务必须最少提前两天完成。“should+have+done”意思是“本来应该做某事，而实际没做。Task是被完成的对象，故用被动语态，选C。