根据观测结果,已建立y关于X的回归方程=2.0+3.0X,则X变化1个单位,y平均变化单位个数为()。
A.1
B.2
C.3
D.4
E.5
参考答案:C
— Mr Smith, may I ask for a few days off? I am worn out.
— _____. We are as busy as a bee. [ ]
A. Don't mention
B. Forget it
C. No, you can't
D. Sure, go ahead
与人体心脏四腔直接相连的血管中,流动脉血的静脉血管是( )
A.肺动脉
B.肺静脉
C.主动脉
D.上下腔静脉