你的问题不太明确.
我试着回答：
英文语法有一句子结构：主+系动词+标语,
例句： They are students. (他们是学生.)
改一般疑问句：Are they students? (他们是学生吗?)
肯定回答：Yes, they are.
否定回答：No, they are not.
They are students. 是肯定句.
They are not students. 是否定句.
系动词变化：
原形：be
现在时态：am, is, are
过去时态：was, were
现在分词：being
过去分词：been
不知是否帮到你!呵呵!