Solidgeometryhasenabledastronomerstocalculatethepositionsoftheheavenlybodiesrelativetooneanother.
A、ontopofFormerly,intheUnitedStates,manynursesworkedasprivatedutynursesratherthaninhospitals.
Thecontrolsofmostmodernairplanescanbeoperatedeithermanuallyorautomatically.
Someseaurchins海胆havevenomous(toxin)spines
ThecompanyissuesanannualreporteveryMarch.
Themegaphone(microphone)makesthevoicesoundlouderbecauseitpointssoundwavesinonedirectionandkeepsthemfromspreadingoutinalldirections.