10.样本数据:-2,-1,0,1,2的方差为( )
| A. | $\sqrt{2}$ | B. | 2 | C. | 1 | D. | 2.5 |
9.若变量x、y满足约束条件$\left\{\begin{array}{l}{x+2y≥0}\\{x-y≤0}\\{x-2y+2≥0}\end{array}\right.$,则z=2x-y+1的最小值等于( )
| A. | -$\frac{5}{2}$ | B. | -2 | C. | -$\frac{3}{2}$ | D. | 2 |
8.若某中学高二年级8个班参加合唱比赛的得分如茎叶图所示,则这组数据的中位数是( )

| A. | 91.5 | B. | 92.5 | C. | 91 | D. | 92 |
7.在空间直角坐标系中,已知点Q(-3,1,4),则点Q关于xOz面的对称点的坐标为( )
0 225566 225574 225580 225584 225590 225592 225596 225602 225604 225610 225616 225620 225622 225626 225632 225634 225640 225644 225646 225650 225652 225656 225658 225660 225661 225662 225664 225665 225666 225668 225670 225674 225676 225680 225682 225686 225692 225694 225700 225704 225706 225710 225716 225722 225724 225730 225734 225736 225742 225746 225752 225760 266669
| A. | (3,-1,-4) | B. | (-3,-1,-4) | C. | (3,1,4) | D. | (-3,-1,4) |