Many entomologists say that campaigns to eradicate the fire ant in the United States have failed because the chemicals that were used were effective only in wiping out the ant's natural enemies, which made it easier for them to spread.
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Awhich made it easier for them
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Bwhich makes it easier for it
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Cthus making it easier for them
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Dthus making it easier for the ant
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Ethereby, it was made easier for the ant
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正确答案: D