第9题: [单项选择]The professor can hardly find sufficient grounds ______ his argument in favor of the new theory. A. which to base on B. on which to base C. to base on which D. which to be based on 参考答案:B 答案解析:定语从句。这里实际指to base his argument on sufficient grounds。句中使用定语从句的形式,先行词为sufficient grounds,对应的关系代词应该为wh