为了考察两个变量x和y之间的线性相关性,甲、乙两位同学各自独立地做100次和150次试验,并且利用线性回归方法,求得回归直线分别为t1和t2,已知两人在试验中发现对变量x的观测数据的平均值都是s,对变量y的观测数据的平均值都是,那么下列说法正确的是( )
A:t1和t2有交点(s,t)
B:t1与t2相交,但交点不一定是(s,t)
C:t1与t2必定平行
D:t1与t2必定重合
中国特色社会主义理论体系是***人在30年的改革实践中形成的,这一理论体系包含的重大战略思想有( )
用方框中所给单词的适当形式填空,使短文通顺、正确、连贯(每个单词限用一次)。
hair, never, old, newspaper, play, but, can't, get, glasses, build
My grandfather is seventy years old, ____ he is still very healthy. He is tall and of medium ____ . He has short straight white ____ He likes reading. Every morning he ____ up very early and then reads morning ____ . When he reads, he always wears ____ . He also likes ____ chess, too. He always plays chess with his ____ friends. He ____ plays chess with me. Why? Because I ____ play chess.
如图所示.将底面积为100cm2,重为5N的容器放在水平桌面上,容器内装有重45N,深40cm的水. 求: