In 1861 it seemed inevitable that the Southern states would break away from the Union.
A、strangeB
暂无解析
Formulatedin1823,theMonroeDoctrineassertedthattheAmericaswerenolongeropentoEuropeancolonization.
Batsfly,ratherthanglide,andthusaretheonlymammalscapableoftrueflight.
ThefirstimportantexpositionintheUnitedStateswasheldinPhiladelphiain1876.
Someanimalspantandsweattospeedevaporationofbodymoistureandthuscoolthemselves.
Someseaurchins海胆havevenomous(toxin)spines
