AlthoughtheCarbon14methodofdatingoldobjectsisnotfoolproof,itisthebestmethodavailableatpresent
A、whollyoperationalInthenortheasternUnitedStates,itrainsintermittently间歇地throughoutthespring.
Withlasersscientistscanprobemanyphysicalprocesses,suchascombustion,oncebeyondourken.视野
Blue－greenalgaegrowabundantlyinsaltmarshes.
Eyespots,themostrudimentaryeyes,arefoundinprotozoan原生动物flagellates鞭毛虫,flatworms扁形虫,andsegmentedworms片段蠕虫.
Formulatedin1823,theMonroeDoctrineassertedthattheAmericaswerenolongeropentoEuropeancolonization.
