同学, must have working hard这个说法是错误的,must have been working hard是一个过去完成进行时,指猜测某人一定在努力工作,这个状态已经进行了很久并将延续下去. 再问： 原题： Amy did best in the English test. She __________ hard last week. A. must have working B. should have worked C. should work D. must work 再答： 嗯，选B. A选项本身结构错误，所以不选。 B选项should +have done情态动词表推测 C、不能表达推测的意思 D、太绝对，本来是推测他上周努力工作了。
