下列变化，属于物理变化的是(  )

    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.

生物都具有一些共同的特征，下列与“植物向光生长”现象具有相同特征的是（  ）