到底神马时候用that 和what (同位语从句中)对比:) I have no idea what has happened to her .(2) Suddenly the thought came to him that he could go blind.这两句中what 和that 可以互换吗?
问题描述：
到底神马时候用that 和what (同位语从句中)
对比:) I have no idea what has happened to her .
(2) Suddenly the thought came to him that he could go blind.
这两句中what 和that 可以互换吗?
答
用what时，从句缺成分，如上句 I have no idea what has happened to her .what作从句的主语，有时也做宾语或表语，因此从句如果缺主语、宾语或表语，就用what;that引导同位语从句时不作成分，只起连接作用。如上句that he could go blind，去掉that，意义完整he could go blind，因此从句意义完整，不缺主语、宾语或表语，就用that.
答
当然不能互换, 这两个都可以引导各种各样的从句, 从句里that有时作成分比如定语从句, 有时不做成分,比如同位语宾语从句. 分不同的从句不同情况, 而what一般都做成分. 建议你买无敌英语语法, 把从句部分从头到尾好好看一遍就能搞得很透彻
答
不能替换,（1）句中what在同位语从句中作主语（从句缺了主语）
（2）句中that只起连接作用（因为从句中不缺成分,也没有疑问）