sed编辑器中，多行命令的使用出现的问题

请各位朋友帮忙看看，这里显示出来的结果为什么是“this is b”重复了呀（为什么不是“this is a”重复呀！它在“this is b”前面呀。或者为什么不是“this is a和this is b”一起重复呢？）非常期待你的解答💐🍭🍭💐

我这里是一起重复啊

   15/11/2022   09:37.09   /home/mobaxterm/Desktop  sed '
> N
> /this\nis/p
> ' data1.txt
this
is a
this
is a
this
is b
this
is b
this
is b
this
is b
this is c
                                                                                            ✓

  15/11/2022   09:37.26   /home/mobaxterm/Desktop  cat data1.txt
this
is a
this
is b
this
is b
this is c
                                                                                            ✓

  15/11/2022   09:37.55   /home/mobaxterm/Desktop 