back and forth 来来回回;反复 He walked back and forth in the room, thinking about the problem. 他在屋里来回走动，思考着问题。 Don't say this back and forth, I know how to do. 不要反复说这个，我知道该怎么做。 A:Please don't go back and forth, I'm doing my homework. 请不要来回走动，我在写作业。 B:Oh, I'm sorry, I didn't notice that you were doing your homework. 哦，对不起，我没注意到你在写作业。