1.He entered the room when (while,as)the meeting was going on.（正当.，表示一段时间) 2.When she comes,I shall tell her to wait for you. 个时间点，不能用while) 3.His mother was just coming along to see him when she ran into his classmate John.(when引导的从句相当于 一个由and连接的并列分句，这里只能用when,意为“在那 时”) 4.I felt somewhat disappointed and was about to leave when something occurred which attracted my attention. (在主句动作进行过程中，从句动作发生了，这是一种主从关 系颠倒的现象) 5.They made no effort to hide their amusement whenever I produced a packet of sweets from my pocket.(指任何 个不具体的时间) Unit 3,Book 4Unit 3, Book 4 1. He entered the room when (while, as) the meeting was going on. （正当.，表示一段时间） 2. When she comes, I shall tell her to wait for you. （表示 一个时间点，不能用while） 3. His mother was just coming along to see him when she ran into his classmate John. （when 引导的从句相当于 一个由and连接的并列分句，这里只能用when，意为“在那 时”） 4. I felt somewhat disappointed and was about to leave when something occurred which attracted my attention. (在主句动作进行过程中，从句动作发生了，这是一种主从关 系颠倒的现象) 5. They made no effort to hide their amusement whenever I produced a packet of sweets from my pocket. （指任何 一个不具体的时间）