1 I am sorry 是不是主系表结构 I am sorry to keep you waiting.句子中的to
1 I am sorry 是不是主系表结构 I am sorry to keep you waiting.句子中的to keep you waiting做什么成分 2 The question is difficult to answer.句子中的to answer做什么成分.是不是有be动词出现都是主系表结构. I am sorry 是主系表结构吗
I am sorry to keep you waiting to keep you waiting 是不定式短语做状语,表原因 The question is difficult to answer to answer 作状语修饰形容词difficult,和difficult一起构成形容词词组在句中作表语.此不定式和句子主语The question 有逻辑上的动宾关系 问题补充: I am sorry 是主系表结构