TheSalkvaccineisamajorfactorinthefighttoeradicatepolio.
A、completelydestroyThemegaphone(microphone)makesthevoicesoundlouderbecauseitpointssoundwavesinonedirectionandkeepsthemfromspreadingoutinalldirections.
Cometsarestillregardedwithawebysomepeople.
InthenortheasternUnitedStates,itrainsintermittently間歇地throughoutthespring.
Formulatedin1823,theMonroeDoctrineassertedthattheAmericaswerenolongeropentoEuropeancolonization.
Alligatorsstillexistinsomeofthedank潮濕swampsandbayous小海灣ofAlabama'scoastalregions.