Therehavebeenmanygreatinventionsorthingsthatchangedthew...
问题详情：Therehavebeenmanygreatinventionsorthingsthatchangedthewaywefirstgreatinventionwastheonethatisstillveryimportanttoday—themadeiteasiertocarryheavythingsandtotravellongdistance.Forhundredsofyear...