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viviansecret

19.   A tree’s age can be determined by counting the annual growth rings in its trunk. Each ring represents one year, and the ring’s thickness reveals the relative amount of rainfall that year. Archaeologists successfully used annual rings to determine the relative ages of ancient tombs at Pazyryk. Each tomb was constructed from freshly cut logs, and the tombs builders were constrained by tradition to use only logs from trees growing in the sacred Pazyryk Valley.

Which one of the following, if true, contributes most to an explanation of the archaeologists’ success in using annual rings to establish the relative ages of the tombs at the Pazyryk site?

(A) The Pazyryk tombs were all robbed during ancient times, but breakage of the tombs seals allowed the seepage of water, which soon froze permanently, thereby preserving the tombs’ remaining artifacts.

(B) The Pazyryk Valley, surrounded by extremely high mountains, has a distinctive yearly pattern of rainfall, and so trees growing in the Pazyryk Valley have annual rings that are quite distinct from trees growing in nearby valleys.

(C) Each log in the Pazyryk tombs has among its rings a distinctive sequence of twelve annual rings representing six drought years followed by three rainy years and three more drought years.

(D) The archaeologists determined that the youngest tree used in any of the tombs was 90 years old and that the oldest tree was 450 years old.

(E) All of the Pazyryk tombs contained cultural artifacts that can be dated to roughly 2300 years ago.

答案：C。这道题虽然做对了，但严重怀疑自己是蒙对的。我不是特别明白的地方在于C的存在可以帮助确定这些logs被砍下来时的年龄，但是这些logs被砍下来后再做成tombs（坟墓）这时候log都已经被砍下来了应该就不会长年轮了吧。这样无法判断出坟墓的年龄啊。请多多指教。。。

viviansecret

Up!

heavennancy

斗胆一试

ring=>each ring/year and thickness=>tree's age

所以结论：

ring=>each ring/year and thickness=>tomb's age

我觉得C补充了特定样本log in the Pazyryk tombs的有效性，其中既包括time又包括thickness，即补充了缺失的中间结论。

欢迎拍砖

viviansecret

感觉C更像加强。。。欢迎大家多指教：）

ARCHER420

先说说楼主的疑问，题干很清楚Each tomb was constructed from freshly cut logs。。。所以你不必怀疑木头还长不长年轮了。都是新鲜的木头马上建造墓穴。

另外，我的理解。题干说年轮的圈数和厚度能帮助确定墓穴的年龄，但是具体怎么确定没说。你想想现在给你个12年的木头，埋在地下，50年后有人挖出来，马上就能说出你是那一年埋下的吗？显然不能。我想考古学家必须根据年轮的幅度（12年）来对比气候记录，来推测那12年是历史上哪一段时间。然后确定最后一个年轮是哪一年。这样就知道坟墓是哪一年建造的了。因为题目说了，坟墓都是用新鲜木头，不耽搁。

照这个思路来看，其他选项就容易排除了。