http://www.9xue.com/Html/200472720938-1.htmlhttp://edu.cyol.com/content/2005-07/07/content_1088205.htmhttp://zxquestion.eastday.com/search/AllQuestions.aspx?roomid=145&abspage=9这三个看完后枣中你就明白凳埋山液枯了..