设C是四分之一圆域:x2+y2≤1,x≥0,y≥0,用极坐标计算二重积分sin(x2+y2)dxdy,其值是()。
A.A
B.B
C.C
D.D
参考答案:D
Everybody _________spend ___________ in bed.
A.has to; some time
B.have to; some time
C.has to; sometimes
D.have to; sometimes
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