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Scientists have been studying different ecologies ______ the 20^th century.

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Ha Long Bay is the product of geological ______ that lasted more than 500 million years.

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The local farmers are trying to stop the invasive species from spreading for the past six months.

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Scientists have been studying the elements that affect the develop of the native species.

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The red squirrel in England is in danger of ______.

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Scientists have been developing practical tools and methods to measure the ______ of the ecosystem.

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Natural resource managers ______ the needs and behaviors of wildlife.

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The national park was established to ______ the ecosystem of the limestone forests.