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本题由lindy提供
2107 次学习

Dendrochronology, the study of tree-ring records to glean information about the past, is possible because each year a tree adds

a new layer of wood between the existing wood and the bark. In temperate and subpolar climates, cells added at the growing season's start are large and thin-walled, but later the new cells that develop are smaller and thick-walled; the growing season is followed by a period of dormancy. When a tree trunk is viewed in cross section, a boundary line is normally visible between the small-celled wood added at the end of the growing season in the previous year and the large-celled spring wood of the following year's growing season. The annual growth pattern appears as a series of larger and larger rings. In wet years rings are broad; during drought years they are narrow, since the trees grow less. Often, ring patterns of dead trees of different, but overlapping, ages can be correlated to provide an extended index of past climate conditions.

However, trees that grew in areas with a steady supply of groundwater show little variation in ring width from year to year; these "complacent" rings tell nothing about changes in climate. And trees in extremely dry regions may go a year or two without adding any rings, thereby introducing uncertainties into the count. Certain species sometimes add more than one ring in a single year, when growth halts temporarily and then starts again.

The passage suggests which of the following about the ring

patterns of two trees that grew in the same area and that were of different, but overlapping, ages?


    (A) The rings corresponding to the overlapping years would often exhibit similar patterns.

    (B) The rings corresponding to the years in which only one of the trees was alive would not reliably indicate the climate conditions of those years.

    (C) The rings corresponding to the overlapping years would exhibit similar patterns only if the trees were of the same species.

    (D) The rings corresponding to the overlapping years could not be complacent rings.

    (E) The rings corresponding to the overlapping years would provide a more reliable index of dry climate conditions than of wet conditions. 


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答案:
A
这道题目有
一定的难度,看似像一个“支持主题”类的题目,但实际上文章并没有明确说明在同一地区的不同年龄的两颗树应该有什么共同点。这个题目定位在第一段最后一句“Often, ring patterns of dead trees of different, but overlapping, ages can be correlated to provide an extended index of past climate conditions.” (A)Correct. 它们重合年龄的年轮通常有相似的形式。第一段在描述一个年轮形成的过程,说明年轮形成过程大体相同,在定位句作者提到,不同年龄的树,只要有共同活着的时间,那么这样的年轮就可以被联系起来提供气候信息。就年轮的成因来说,每年的年轮由于气候等原因应该是不一样的。每棵树的大小,粗细等都有不同,这样年轮不会有标准化的粗细之分,所以只能通过相对的年轮模式的相似性来判断相对的那些年的气候。如果任意一颗树在相同的时间段内的年轮模式也不相似,则定位句的意义就不存在了,因为如果什么都不相似,也就没有任何东西可以互相联系了。 (B)和只有一颗树活着的年份相符的年轮不能说明那些年的气候情况。只要两棵树有共同活着的年份,那么其他任何的这颗树的年轮都可以通过其粗细来显示气候。所以就算在有些年只有一棵树活着,该树的年轮也可以反映那些年的气候。 (C)只有同种类的树木在共同活着的年份中才能有模式相似的年轮。文中并没有提到一定要同种的树木。 (D)在重合年份的树木的年轮不能是“complacent”的年轮。这个选项很有迷惑性。细读文中第一段可知,为什么定位句说用两颗树的年轮才能判断判断气候信息,是因为其实是用“非重叠”的年轮来判断气候的。如果用两棵树相似部分的年轮来判断气候的话,那么也就不必要用两颗树了。所以,“重叠”年份的年轮是不是“complacent”并无所谓,只要其他的年轮不是“complacent”的就可以了。 (E)年轮在湿润的条件下比干燥的条件更能可靠的反应当时的气候。这个选项可以定位在“In wet years rings are broad; during drought years they are narrow, since the trees grow less”。文中没有提到证据证明湿润气候比干燥气候更加的可靠。

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