1.How many is left?
2.There remain 3 of us./Three apples are left.
3.We still have 3 books./We have another three books.
过去分词相当于形容词的语法功能,可以作定语、表语、补足语和状语.
Something is left在不同的语境中可以是主系表结构或者是被动语态.到底是系表结构还是被动语态,要看具体的语境,只表示剩余、留下的状态,则是系表结构；上下文需要表示被谁留下的意思,则是被被动语态.