Question

【题目】Students are supposed to ______ the blackboard before ______ the next class.

A. clean the chalk, began B. clean the chalk off, began

C. clean the chalk off, beginning D. clean the chalk off, begun

Answer 1

【答案】C

【解析】

句意：学生应该在下节课开始前把黑板上的粉笔擦干净。短语be supposed to do sth.表示应该做某事；before是介词，后加动名词，clean the chalk off,表示把粉笔擦掉；begin the next class.表示下节课开始。根据题意，故选C。