求问！OG17 587

mengtian0803

587. Rainwater contains hydrogen of a heavy form called deuterium. The deuterium content of wood reflects the deuterium content of rainwater available to trees during their growth. Wood from trees that grew between 16,000 and 24,000 years ago in North America contains significantly more deuterium than wood from trees growing today. But water trapped in several North American caves that formed during that same early period contains significantly less deuterium than rainwater in North America contains today.

Which of the following, if true, most helps to reconcile the two findings?

(A) There is little deuterium in the North American caves other than the deuterium in the water trapped there.

(B) Exposure to water after a tree has died does not change the deuterium content of the wood.

(C) Industrialization in North America over the past 1 0 0 years has altered the deuterium content of rain.

(D) Trees draw on shallow groundwater from rain that falls during their growth, whereas water trapped in caves may have fallen as rainwater thousands of years before the caves formed.

(E) Wood with a high deuterium content is no more likely to remain preserved for long periods than is wood with a low deuterium content.

正确答案是选D，可是我搞不清楚D的意思是什么，还有为什么E不对呢？

第一次在论坛发帖，求大神解答！！！

万分感谢！

Fiona09

版上Helr大神对此题的解释：https://gmat.la/question/OG2017-CR-587

mengtian0803

Fiona09 发表于 2017-6-12 15:54
版上Helr大神对此题的解释：https://gmat.la/question/OG2017-CR-587

懂了！！感激！

CathyGYM

求问这题的解释！

标答给的是B，但是我不太想的明白。
B确实加强了第二种假说，但是没有削弱第一种假说啊！

abbylung

我的想法

P：树木中D反应雨水中D，以前树木中D比今天树木D多
C：但是同时期形成的洞穴积水D比今天雨水D少

Gap：今天树木对今天雨水，以前树木应该对同时期雨水，但是这里以前树木对同时期形成的洞穴积水

D 树吸收地下雨水，（将今天树木和今天雨水联系起来）但是洞穴积水是洞穴形成数千年前的雨水（切断以前树木和同时期雨水联系）

深高金的zkk

abbylung 发表于 2020-4-15 10:33
我的想法

P：树木中D反应雨水中D，以前树木中D比今天树木D多

我理解这两个的选项的区别 导致这两个的题干的区别。
可是我不明白，为什么洞穴的水是很早很早很早之前形成的，洞穴的d的含量就少了呢？？？不应该洞穴积水，越积越多，d应该更多么？

ST5

深高金的zkk 发表于 2020-9-2 22:29
我理解这两个的选项的区别 导致这两个的题干的区别。
可是我不明白，为什么洞穴的水是很早很早很早之前形 ...

你的doubt是可能的，D并没有直接完全completely reconcile这两个现象，因为如果cave接受的是很早以前rain，rain的D浓度到底是更多还是更少是不知道的，但是D为解释这个现象open了door。
你的后一段是错误的D content指的是浓度，不是绝对多少。