Solidgeometryhasenabledastronomerstocalculatethepositionsoftheheavenlybodiesrelativetooneanother.
A、ontopofInthenortheasternUnitedStates,itrainsintermittently間歇地throughoutthespring.
AlthoughtheCarbon14methodofdatingoldobjectsisnotfoolproof,itisthebestmethodavailableatpresent
Thecontrolsofmostmodernairplanescanbeoperatedeithermanuallyorautomatically.
Formulatedin1823,theMonroeDoctrineassertedthattheAmericaswerenolongeropentoEuropeancolonization.
Thewheelsofthefirstroadvehicleswerefashionedfromcrudestonedisks.