想请教一下WHAT从句的主谓一致问题

落地oo花开

   what引导的名词性从句做主语时，主句谓语动词的单复数情况：
(1)What在从句中做主语，主句谓语由what从句谓语决定。
What he’d like most for a birthday present is a camera.
(2)what在从句中做宾语，主句谓语由主句表语/宾语决定
what they want are XX,XX&XX。
What his father left him are a few English books.
怎么判断what从句是做主语还是宾语？