是系表结构。
系表结构有两部分构成:连系动词和表语
连系动词分为三类:be 动词,感官动词,趋势动词。
1) Be 动词:am, is, are, was, were
2) 感官动词:sound, look, taste, feel, smell
3) 趋势动词:appear, become, grow, get, turn, seem, remain
下列成分都可以做表语:名词, 形容词,副词, 动词不定式,动名词,现在分词,过去分词,表语从句.
(注意:连系动词不能够单独作谓语,他们必须和表语一起构成谓语):
参考资料:http://zhidao.baidu.com/question/11585732.html