此题就是不知道怎样用造坟用的木头来测坟龄，难道树被砍了之后年轮还继续长？？？参考答案是c
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.
重新看了一下问题，问的是"relatie age", 开始时我误认为 "absolute age”55555555555555555555555555555555555
Actually I do not think lawyer_1's explanation is accurate. Acutally "c" is correct because it emphasizes that the sequence of " six drought years followed by three rainy years and three more drought years" is very distinctive.
Before the archelogists began to investigate the age of the tombs, they had been aware of the pattern of clamate change in the Pazaryze Valley. ( actually that is why the author has to emphasizes "use only logs from trees growing in the sacred Pazyryk Valley.") The sequence of the twelves is unique in the history of the Valley. And the tree rings exactly indicates such a sequence. Therefore, those archaelogists can use the information from rings to eximate the age of the tomb.
So the problem for you is not ignoring the difference between "absolute age" and "relative age". For such a question, the right answer may not be the reasonal at the first glance. But it is definately an answer that can help to bridge the gap in the argument. Hope this makes a sense to you.
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