ZhangFang’sparentsarebothteachers.Theyarealwaysbusy

問題詳情：

Zhang Fang’s parents are both teachers. They are always busy ________ into deep night.

    A. work           B. working        C.  worked         D. to work

【回答】

B

知識點：動詞和動詞短語

題型：選擇題