多项式x4-3x3+9x+2与多项式3x3-x4+8-4x的和一定是[ ]
A.偶数
B.奇数
C.2与5的倍数
D.以上答案都不对
答案：D
— Would you care for a drink?
— No, thanks.I________. [ ]
A. would rather not
B. wouldn't like to
C. would like to
D. prefer to have one
在初步确定年调节和多年调节水电站装机规模时，其经济利用小时数常取（）h。
A.1500～2500
B.2500～3500
C.3500～4500
D.4500～5500
