,孙老师，您好，我正在学习您的高中英语语法，有点疑惑,就是您讲的内容好像比较简单，一些特殊的语法现象没有提及，而语法书上的很复杂，比如说“定语从句中什么时候用which 什么时候用that”这一类的东西语法书上还有很多，您认为需要花时间记忆这些吗？

,▲ 必须使用关系代词that的几种情况1. 先行词被形容词最高级修饰。● This is the worst book that I have read.● He is the tallest man that I know.2. 先行词是all, everything、nothing、something等不定代词● He told me all that he knew.3. 当先行词被only, any, no, very, little或序数词修饰时。● That is the only way that leads into the mountain.● Who is the first student that came here?

谢谢老师的回答。类似这样的特殊情况语法书上总结了许多，请问这些都需要记忆吗？