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