I live in a nice new building in Beijing. It is very tall. It has eighteen floors. There are about eighty families in the building. That is to say (也就是说), about two hundred and forty people live in the building.

    My home is on the twelfth floor. We have two bedrooms and a living room. They are big and clean. There are a lot of big trees and beautiful flowers around our building. I like looking out of the window in my room. I can see cars and buses running in the street. I can see people walking in the street, too. They look so small! I can also see a lot of tall buildings. How beautiful Beijing is! I am happy to live in this nice, new and tall building.

如图所示，在水平地面上的磁体上方，有挂在弹簧测力计上的小磁体（下部N极）．小辉提着弹簧测力计向右缓慢移动，挂在弹簧测力计上的小磁体下端，沿图示水平路线从A缓慢移到B．则图乙中能反映弹簧测力计示数F随位置变化的是(    )

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下列生物中不属于单细胞生物的是（    ）

某相对封闭的山区，有一种发病率极高的遗传病，该病受一对等位基因A—a控制。调查发现：双亲均为患者的多个家庭中，后代的男女比例约为1∶1，其中女性均为患者，男性中患者约占3/4。下列相关分析中，错误的是（    ）