如图，在直角坐标系中，正方形EFOH是正方形ABCD经过位似变换得到的，对角线OE=4$\sqrt{2}$则位似中心的坐标是

C

    Hi! I'm Alan. This is my dream house (梦幻屋). It has a small but nice room. Some pictures are on the wall. There is (有)a bookcase in my room. There is a desk and a chair in it. My schoolbag is on the desk. Oh! Where is my pencil case? It is under the chair. There are some pencils and a ruler in the pencil case. My shoes and a basketball are under the bed. I like my dream house very much.

句子：今天下三分，益州疲弊，此诚危急存亡之秋也。

对以自然选择学说为核心的现代生物进化理论，正确的理解是（　　）

①环境改变使生物产生适应性的变异；

②隔离是新物种形成的必要条件；

③变异是不定向的；

④变异是定向的

⑤自然选择使种群的基因频率定向改变并决定生物进化的方向．