What surprised me most was that he had been married.(what在从句中作主语)
What you told me this morning is unbelievable.(what 在从句中作宾语)
What his phone number is is still unknown to me.(what在从句中作宾语)
That he was late for school again this morning made the teacher angry.(that 在名词性从句中都是不作成分,没有意思的.)