鹤管与集油管的连接方式有（）（）、（）三种。
参考答案：专用单鹤管式、两用（多用）单鹤管式、双鹤管式
人民群众向政府表达意愿的制度不包括（）
A.信息公开制度
B.请愿制度
C.信访制度
D.申诉制度
Over the last three years a scientist had an average (arithmetic mean) yearly in come of $45,000. The scientist earned 1 times as much the second year as the first year and times as much the third year as the first year. What was the scientist’s income the second year ？
times as much the second year as the first year and 
times as much the third year as the first year. What was the scientist’s income the second year ？