Question

5. The students        when Miss Brown went to get a book she had left in the office. (busily)

当Brown小姐去拿她那本落在办公室的书时，学生们正忙着做作业。

Answer 1

5. were doing their homework busily此处应用过去进行时，表示过去特定时间里正发生的事情。另外，注意homework为不可数名词。