Insect pests are among the leading causes of crop failure.
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Formulatedin1823,theMonroeDoctrineassertedthattheAmericaswerenolongeropentoEuropeancolonization.
The megaphone(microphone) makes the voice sound louder because it points sound waves in one direction and keeps them from spreading out in all directions.
The flower bud of a water lily 百合 opens at sunset since .its opening is triggered(commence) .by the decreased light.
Urbanrenewalprogramsstrivetoupgradeareasthatarebecomingslums.
TheNativeAmericaninterpreterSacajaweawasavaluablememberoftheLewisanddarkexpeditionin1805.