观察和体会下列对话：
A:She's crying sadly.
B:Do you know what is the matter with her?
= ...what is wrong with her?实际上,the matter = wrong,adj.是形容词
这个宾语从句的结构是:...what 引导宾语从句的连接词兼主语,is,be 动词,the matter with her,是 adj.短语,作表语,即,这个宾语从句是个“系表结构”.
只要明白,the matter = wrong,adj.你就明白为什么是这样的“系表结构”了.
Do you know what wrong (adj) is with her?
所以也不能说：Do you know what the matter (adj.)is with her?
= ...what the trouble is with her?
但是,不说,.what is the trouble with her?
因为,the trouble 不说 adj.短语,而是一个普通的“名词短语”
这样的宾语从句的语序是：...what 连接词,the trouble 名词短语作主语,is 动词……
A:I guess that's because she failed the test.
再看：
A:She's crying sadly..
B.Is there anything the matter with her?( ...anything + adj.)
=Is there anything wrong with her?
从这种表达中更能看出,the matter = wrong,的 adj.词性.
A.I guess.