表语
表语是用来说明主语的身份、性质、品性、特征和状态的,表语常由名词、形容词、副词、介词短语、不定式、动词的-ing、从句来充当,它常位于连系动词（be,become,appear,seem等）之后.
一.名词作表语
Africa is a big continent.
非洲是个大洲.
That remains is a puzzle to me.
这对我还是个难题.
二.代词作表语
What’s your fax number?