可以有两种,一个是否定主句,即
You don't know that I have a few friends in the class.
你不知道,我在班级有几个朋友.
另一种是否定宾语从句,即
You know that I don't have any friends in the class.
你知道,我在班级没有任何朋友.只有两个空那 you know thatI_don"thave friends in the class可以么可以