从地面竖直上抛一个质量为m的小球，小球上升的最大高度为H，设上升过程中空气阻力f恒定．对于小球从抛出到上升至最高处的过程，下列说法正确的是（   ）

如图表示不同化学元素所组成的化合物，以下说法不正确的是（　　）

    Most American families are smaller than the families in other countries.
Children in the USA will 1 their parents' home when they grow up. They usually live far from their parents because they often goo to different places to find good jobs. They often  2 to their parents or phone them, and they can choose their own 3.  Americans think it's important for young people to make their own decisions.
    Children are asked to do some house work at  4. In many families, children are paid for 5 the housework so that they can learn how to manage their own money.

有一小段通电导线，长为10cm，电流强度为0.5A，把它置于磁场中某点，受到的磁场力为0.1N，则该点的磁感应强度B一定是         （）