A:二月28天
B:平年下半年和闰年下半年天数相等
They __________ go back home __________ they finished cleaning their classroom.
已知:,在NH4CuSO4中加入足量3mol/L硫酸后,下列叙述正确的是 ( )
已知回归直线斜率的估计值是1.23,样本平均数x-=4,y-=5,则该回归直线方程为( )