4. What is the main idea of this passage?
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A
Beavers may be hard-working animals, but they don't always choose the most efficient mechanisms.
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B
Beavers are excellent dam builders.
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C
New Hampshire was the site of the largest beaver dam.
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D
Beavers are well-developed tree cutters.
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E
Beavers are poor surveyors of aquatic environments in some cases.