不是,是同位语从句.
that 引导的同位语从句来解释it那怎样它就成了一个宾语从句了？I know the sentence's mean that my classmates want to know.可以吗原来那个句子把it去掉，i know that classmates XXXXX这个就是that引导的宾语从句了。或者你给的第二个句子里也是宾语从句，不过最好说成I know that the sentences mean that my classmates want to know.这个是双宾语从句，双宾语从句中第一个that不能省略的