They received demands that the work at once.A. must be doneB. would be doneC. had been do

问题补充：

They received demands that the work at once.

A. must be done

B. would be done

C. had been done

D. be done

答案：

A. must be done

B. would be done

C. had been done

(答案→)D. be done

解析：考察虚拟语气。名词demand后面的同位语从句中要使用虚拟语气，使用should+动词原形；should可以省略。句意：他们收到这个命令，这份工作要立刻被做。故D正确。