（ ）the teacher came in, they were talking and laughing. A.wh

你好.答案是B
合并下列句子,如果你会,你在这方面的问题就解决了：
He was getting off the bus. He fell and hurt himself
1 While he was getting off the bus,he fell and hurt himself
2 When he fell and hurt himself,he was getting off the bus
3 He was getting off the bus when he fell and hurt himself
4 He fell and hurt himself while he was getting off the bus.
5 As he got off the bus, he fell and hurt himself
6 He fell and hurt himself as he got off the bus.
简单易懂,没有长篇大论,不过你需要比较和记住.

B when 引导的从句动词可以使延续性和非延续性的。

when
助你学习进步

when 引导的时间状语从句

when