Bob is waiting us in the classroom 哪里有错?
问题描述：
Bob is waiting us in the classroom 哪里有错?
这句中,哪里错了? 是is 还是 waiting 还是 in 还是classroom?
还有一句
What are you talking?哪里错了?
答
waiting -> waiting for等待 (wait 是不及物动词,）
What are you talking about?( talk 是不及物动词,talk about '谈论',