The fertility rate is the number of children a woman can expect during her lifetime; 2.1 is the replacement level, the point at which the population stabilises.
人口出生率是指女性一生预期生养的儿童数目；2.1是更替水平，人口在这一点上保持稳定。
2
Such a concentration of uranium means the lifetime cancer risk in the village was more than 153 times higher than in the normal population.
如此高的铀浓度意味着该村庄的人患终身癌症的风险超过普通人群的153倍。
3
In my father's lifetime, the world's population went from 2 billion to 6 billion-so my father was alive for a tripling of the total human population.