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题目材料：
In the shallow end of Lake Tomwa, there are remains of numerous Jeffery pine trees that grew there during a lengthy drought. Researchers had believed that this drought lasted at least 150 years, but carbon dating reveals that pines were growing in the lake bed for only 120 years, from 1200 until 1320. Since the Jeffrey pines, which cannot survive in water, must have died at the end of the drought, the dating shows that the drought lasted less than 150 years.
The argument given relies on which of the following as an assumption?
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ANo other species of tree started growing in the bed of Lake Tomwa after 1200.
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BNo tree remains of any kind are present at the bottom of deeper parts of Lake Tomwa.
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CThere was at least one tree in the lake bed that was alive for the entire period from 1200 to 1320.
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DThere has not been a more recent drought that caused a drying up of the shallow end of the lake.
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EThe shallow end of the lake had been dry for less than 30 years by the time Jeffrey pines started growing in the lake bed.
E显示答案
