在如图所示的图形中,A弧长为多少?()
A.80.89
B.88.09
C.40.44
D.45.04
参考答案:A
Tom does speak Chinese well, but his reading and writing skills leave much ______. [ ]
A. to improve
B. to be improved
C. being improved
D. having improved
根据样本资料得到单位产品成本y(元)与产量x(万件)之间的回归方程为y=868-8x,则下列说法正确的是()。
A、产量为1万件时,单位成本平均为860元
B、产量为1万件时,单位成本为860元
C、产量与成本之间是正相关关系
D、产量每增加1万件,单位成本增加8元