题目

 It’s amazing that Mike should get such good marks while he does only ________ the others.    A. as much as half   B. as many as half         C. half as much as  D. half as many as 答案：C甲升降机比乙升降机的机械效率高，它们分别把相同质量的物体匀速提升相同的高度．两者相比，甲升降机（ ）A．电动机做的总功较少B．电动机做的总功较多C．提升重物做的有用功较少D．提升重物做的有用功较多