Aboutacenturyago,theaveragelife-span(寿命)forAmericanswas...
问题详情：Aboutacenturyago,theaveragelife-span(寿命)forAmericanswasabout50years.Today,thetypicalAmericanlivesforaroundseventy-eightyears.AccordingtoaGermanagingstudy,themaximumlifespaninindustrializedco...