Audrey Hepburn was born in Belgium _____ 4th May 1929. [ ]
A. at
B. in
C. on
D. from
答案:C
求由曲线xy=1及直线y=x,y=2所围图形的面积A.
用于大面积场地平整,开挖大型基坑,填筑堤坝和路基的机器是()。
A.铲运机
B.正铲挖土机
C.反铲挖土机
D.拉铲挖土机