题目

You can see eighty percent(百分之) of the class ____ most of the work. The rest of the work ________ really difficult.A. is doing, is B. are doing, are C. are doing, is D. is doing, are 答案：【答案】C【解析】句意：你可以看到百分之八十的学生正在做大部分的工作。剩下的工作真的很难。考查系动词辨析。前句是宾语从句，从句主语eighty percent of the class（百分之八十的学生）是复数人称，系词需用are，可排除AD两项；后句 The rest of the work是单数人称，系词需用is。根据句意结构，可知选C某钢丝绳能够承受的最大拉力是4×104N，用它能否一次提起体积为0.5m3的实心铁块？（ρ铁＝7.9×103kg/m3）