The controls of most modern airplanes can be operated either manually or automatically.
A、bythebookD
暂无解析
Blue-greenalgaegrowabundantlyinsaltmarshes.
Someseaurchins海胆havevenomous(toxin)spines
ThefuturesurvivalofthebaldeagleisstillanimportantAmericanecologicalconcern.
Thefearofsmallpox,whichterrorizedtheeighteenthcentury,hasnoanalogy(likeness)today.
Formerly,intheUnitedStates,manynursesworkedasprivatedutynursesratherthaninhospitals.