The first important exposition in the United States was held in Philadelphia in 1876.
A、exhibitionA
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Insectpestsareamongtheleadingcausesofcropfailure.
Formerly,intheUnitedStates,manynursesworkedasprivatedutynursesratherthaninhospitals.
TheSalkvaccineisamajorfactorinthefighttoeradicatepolio.
In1861itseemedinevitablethattheSouthernstateswouldbreakawayfromtheUnion.
Someanimalspantandsweattospeedevaporationofbodymoistureandthuscoolthemselves.
