矩阵$A=\left(\begin{array}{cc}1& 0\\ 0& 2\end{array}\right)$，向量$\overrightarrow{\alpha }=\left(\begin{array}{c}1\\ 2\end{array}\right)$，则$A^{10}\overrightarrow{\alpha }$= （ 　　）

阅读短文，掌握大意，然后从A、B、C、D四个选项中，选出可以填入空白处的最佳选项。

    A little sports shop is near my house. It sells (卖) many good things for  1 . At the shop, we can buy soccer balls,  2 , basketballs and so on. Today my  3 and I go to the4  to buy a tennis racket. There are a lot of 5 . And they have different  6   . I think every racket  7  very nice. My sister chooses (选择) a black one, because black is her favorite8  . You know, my sister is a big sports fan. She has a great sports    9   at home-five soccer balls, four basketballs and many tennis balls. She really likes   10  sports.

如图所示是小明自制的水平仪，它由两条相互垂直的木条加上一根重垂线组成，用它能检查桌面是否水平，该水平仪利用重力方向____ 的原理．