Mr Smith is come from america,so is helen.哪错了,为什么?

Mr Smith is come from america,so is helen.哪错了,为什么? Mr Smith is from America.(改为同义句） Mr.smith is an_(America)d0ct0r Mr Smith is an English teacher. He comes from America. He ha helen is from america对america进行提问什么helen from? Helen is from America.She is A______.(语句通顺） I come from England,but rachael (is from)America.为什么不能填come Mr king___(come)from America. 填空：1.Julia is from America and Helen is from England .They a Mr Smith is walking. What is Mr Smith? The boy is from America.这句话中的from可不可以换成come from?为什么,拜托讲细些.多