题目

—Is your sister helpful at home? ( )—______A.Yes, he is. B.No, she is. C.Yes, she is. 答案：【答案】C【解析】句意：—你姐姐在家有帮助吗？—_____。主语是your sister，故答语用she代替，其肯定回答为Yes, she is. 否定回答为No, she isn't. 故选C。8．中国的西部大开发已经启动，为了避免走先污染后治理的弯路，环保观念和措施应贯彻西部开发的始终．请你谈谈在西部开发过程中为了避免水污染应该注意哪些方面的问题．