人口零增长意味着在一定时间内，出生人数与死亡人数相等，维持人口总量稳定。青梅竹马是消防员风车

　　In the not too distant future, a very smoggy and overpopulated Earth government makes it illegal to have children for a generation. One couple, unsatisfied with their substitute robot baby, breaks the rules and gets in a lot of trouble. (Z.P.G. stands for Zero Population Growth).