Question

When Mr. Li came in and saw the clean and tidy classroom, he was very satisfied and praised the students who were______________.

A.on time B.on business C.on duty

Answer

C

【解析】

句意：当李老师走进来看到干净又整洁的教室时，他很满意，并且表扬了值日的学生。

考查介词短语辨析。on time准时；on business出差；on duty值日。根据前文“the clean and tidy classroom”可知，此处指表扬了值日的学生。故选C。

错因①考生未能抓住句中的关键信息“the clean and tidy classroom”从而未能判定出此处所填介词短语与打扫卫生有关；②不了解三个选项所对应的具体语境；③未结合生活和学习常识判定。