From nowadays, the world have more and more people, somebody say that when in 2015, the population of the world will achieve about 70 billion. General to say, developing country have much more population and increase than the advance country. The population have brouht many seniors problem ,for example :traffic jams，pollution of the environment，the resources are not enough for us,and so populations problem is to become the most serious probelm of the efore,control the population are the one of the biggest problem of the worlds.
