读了《大学英语》１９９７年第１期上陆振惠老师的文章，觉得对指导学生学习ｗｈｅｎ的用法很有帮助。但对其中第９点想作一些补充。ｗｈｅｎ一般引出副词性从句，表示主句行为发生的时间，这时ｗｈｅｎ从句可放在主句前面，也可以放在主句后面，句子的重心都在主句上。但... After reading the article in the first issue of “College English” (1997), Mr. Lu Zhenhui, I feel that it is helpful to guide students in learning how to use it. However, I would like to add something to the 9th point. When it generally leads to adverbial clauses, it indicates when the main sentence acts. At this time, the when clause can be placed in front of the main sentence or behind the main sentence. The sentence’s center of gravity is on the main sentence. but...