AlthoughtheCarbon14methodofdatingoldobjectsisnotfoolproof,itisthebestmethodavailableatpresent
A、whollyoperationalFormerly,intheUnitedStates,manynursesworkedasprivatedutynursesratherthaninhospitals.
TheNativeAmericaninterpreterSacajaweawasavaluablememberoftheLewisanddarkexpeditionin1805.
InthenortheasternUnitedStates,itrainsintermittently间歇地throughoutthespring.
DoubleEagleinthefirsttransatlanticballoon,wasgreetedbyavidcrowdsinFrance.
Someseaurchins海胆havevenomous(toxin)spines
