there is something I need to tell you,sir.The thing is ,I forget to bring my homework.

问题描述:

there is something I need to tell you,sir.The thing is ,I forget to bring my homework.
我想知道这里的The thing is 是插入语吗?那换成 It is,This is 或者 Which is可以吗?麻烦大家帮我讲解下,

The thing is 不是插入语,The thing 是第二句的主语,is 是系动词,I forget to bring my homework 是表语从句,它和系动词一起构成谓语.
换成 It is 还可以.
不可以换成This is,因为this用来启下;可以用that is,因为that用于承上.
换成 which is 可以,但是两句合并成一句,后面那句成了定语从句:
There is something I need to tell you,sir,which is (that) I forget to bring my homework.不过更像书面语.