________________________(下课的时候), we began our writing. John sings________________(边走). _________________________(我们看电视的时候), he was writing a composition.
When the lesson was over
as he walks
While we were watching TV
注意:
1. when, as, while 的区别
when: 持续性/非持续性动词都可 as: 当;一边…一边;随着 while:持续性动词/ 进行