已知全集U=R,集合$A=\left\{x|y=\sqrt{x^2-2x}\right\}$，$B=\left\{y|y=2^x,x\in R\right\}$，则$A\cap B$等于(    )

如图所示，球A在斜面上，被竖直挡板挡住而处于静止状态，关于球A所受的弹力，以下说法正确的是（    ）

①在人类对金属材料的使用过程中，性质活泼的金属单质最早被人们冶炼和使用；

②纯铁比生铁抗腐蚀性更强；

③单质铝在空气中比较耐腐蚀，所以铝是不活泼金属；

④正常人体缺钙会引起骨质疏松症，缺铁会引起贫血等疾病；

⑤青铜、不锈钢、硬铝都是合金；

⑥可通过焰色反应区分钾元素和钠元素．

    On the first day of school, the Nottingham School asked more than 50 students to go home, because the students didn't wear the right clothes. The headteacher said it was an important life lesson for children, though some parents didn't think so.

    In fact, on their first day back from the summer holidays, about 100 students didn't wear the right clothes, so the teachers asked them to stay outside the classroom on the first day. The school made calls to the parents, and 56% of the students went home to change their clothes.

    The Nottingham School started to make its students wear the right clothes in 2013. The headteacher, Dave Hooker said, “Wearing the right clothes, at school or work, is an important lesson for their lives.”

根据短文内容，故答案选择正确答案。

下图是某同学制作洋葱鳞片叶表皮细胞临时装片的步骤图，据图回答：