为什么下面的这样句子中都要加be? 1.He is going to be sick. 2.She can't be out. 3.You must be quiet.
问题描述：
为什么下面的这样句子中都要加be? 1.He is going to be sick. 2.She can't be out. 3.You must be quiet.
请大家详细指教一下
答
因为有形容词或副词.
sick,quiet是形容词,out 是副词.在这两类词前面要加be用词.
比如：He must be happy.（happy是形容词）