Multiple choice

Directions: For this question, select the best of the answer choices given.

Mud from a lake on an uninhabited wooded island in northern Lake Superior contains toxic chemicals, including toxaphene, a banned pesticide for cotton that previously was manufactured and used, not in nearby regions of Canada or the northern United States, but in the southern United States. No dumping has occurred on the island. The island lake is sufficiently elevated that water from Lake Superior does not reach it. The statements above, if true, most strongly support which of the following hypothesis?

  1. The waters of the island lake are more severely polluted than those of Lake Superior.

  2. The toxaphene was carried to the island in the atmosphere by winds.

  3. Banning chemicals such as toxaphene does not aid the natural environment.

  4. Toxaphene has adverse effects on human beings but not on other organisms.

  5. Concentrations of toxaphene in the soil of cotton-growing regions are not sufficient to be measurable.
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B Correct answer
Explanation

Given that toxaphene was used in the southern United States but not in nearby regions of Canada or northern US, and the isolated island lake has elevated terrain preventing water contamination from Lake Superior, atmospheric transport by wind is the most logical explanation for how the pesticide reached the remote location. This phenomenon is known as atmospheric deposition or long-range atmospheric transport of pollutants. The other options are either not supported by the facts or make unsupported claims.

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