求教PREP1 RC1 Essay 15

vansonkated

Essay #15.  341   

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（相关的）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.

Question #52.  341-04   
The passage is primarily concerned with

(A) evaluating the effect of climate on the growth of trees of different species
(B) questioning the validity of a method used to study tree-ring records
(C) explaining how climatic conditions can be deduced from tree-ring patterns
(D) outlining the relation between tree size and cell structure within the tree
(E) tracing the development of a scientific method of analyzing tree-ring patterns


正确答案是选C，想问选B为什么不对，文章开头明明有说一个
a method used to study tree-ring records，为什么不为中心句呢？况且第二段有however，说明questioning ？？
请教高手~

JoshwuS

同问！！高手帮帮忙好吗

我也是选的B
B 质疑树木年轮研究方法的正确性
C 解释气候条件如何从树木年轮模式上推断出来

我觉得B是文章第二段的中心，C是第一段的中心
整个文章的重点应该放在第二段，即however后面，可是为什么会选择C呢？？

arthurman

个人理解

这篇文 不是在谈 树怎么怎么了，注意这句 to glean information about the past  文章中心是说树和气候，由树的年轮来推气候的情况 所以B 错在used to study tree-ring records。

JoshwuS

有道理
现在再想想，发现主旨题答案里必须有文章的核心词
及气候和年轮，那么B只有年轮，C把两者都包括进去了，是更好的答案

linglingdan

However 不是在质疑method有问题，而是说某些树无法从年轮上看出我们想得到的信息。这个结果是客观的，不分对错，从作者陈述的语气上也可以看出来。更不能由此推出得到这个结果的方法是错误的，因此不好说整篇文章是在questioning。
反而是通篇文章介绍了各种各样的年轮以及背后的意义，看起来不是更像科普读物吗~所以个人意见文章只是单纯、中立地在陈述一些客观的事实。