考点一 While the boy was walking down the street, the UFO landed.(P19)
【用法归纳】辨析while与when
when和while都用来引导时间状语从句，表示“当什么时候”。两者的区别有：while相当于during the time，意思是“在什么期间，和什么同时”，其后只能跟延续性动词；when相当于at/during the time, 从句中的谓语动词可以是延续性动词，也可以是非延续性动词。如：
While I was cooking, someone called. 当我在做饭的时候，有人打电话过来。
He was sleeping when I came in. 当我进来时他正在睡觉。
When he was a child, he loved many interesting things. 当他还是个孩子时，他就喜欢许多有趣的事物。
考点二 I had a very unusual experience on Sunday.星期天我有一段非同寻常的经历。(P20)
