我在百度知道里看到what,who可以引导同位语从句,不太理解.
有个例句是The question who will take his place is still not clear.I have no idea what size shoes she wears.这两个词都在句中做成分,而如果以that引导同位语从句,that不做成分,去掉后从句还是一句完整的话.那怎么断定what ,who 引导的是同位语从句而不是其他.