人物：先行词既有人又有物时
Students talked about persons and things that they saw in Yanxigonglue.
I can remember persons and things that I saw in the room.
高：先行词被形容词最高级修饰时
She is the most beautiful girl that I have ever seen.
This is the most interesting film that I have ever seen.
序：先行词被序数词修饰时；
This is the last thing that I want to do.
The first letter that I got from him will be kept.