请教GWD-12-Q29的逻辑题

梦想守护者

The Earth’s rivers constantly carry dissolved salts into its oceans.  Clearly, therefore, by taking the resulting increase in salt levels in the oceans over the past hundred years and then determining how many centuries of such increases it would have taken the oceans to reach current salt levels from a hypothetical initial salt-free state, the maximum age of the Earth’s oceans can be accurately estimated.

Which of the following is an assumption on which the argument depends?

A.    The quantities of dissolved salts deposited by rivers in the Earth’s oceans have not been unusually large during the past hundred years.
B.    At any given time, all the Earth’s rivers have about the same salt levels.
C.    There are salts that leach into the Earth’s oceans directly from the ocean floor.
D.    There is no method superior to that based on salt levels for estimating the maximum age of the Earth’s oceans.
E.    None of the salts carried into the Earth’s oceans by rivers are used up by biological activity in the oceans.

答案是A，但是取反之后，想不通是怎么反驳原文的，希望各位牛人能详细帮忙解释一下（最好每个选项都说明一下），不胜感激！！

vivianzhili

The Earth’s rivers constantly carry dissolved salts into its oceans.  Clearly, therefore, by taking the resulting increase in salt levels in the oceans over the past hundred years and then determining how many centuries of such increases it would have taken the oceans to reach current salt levels from a hypothetical initial salt-free state, the maximum age of the Earth’s oceans can be accurately estimated.

Which of the following is an assumption on which the argument depends?

A.    The quantities of dissolved salts deposited by rivers in the Earth’s oceans have not been unusually large during the past hundred years.
B.    At any given time, all the Earth’s rivers have about the same salt levels.
C.    There are salts that leach into the Earth’s oceans directly from the ocean floor.
D.    There is no method superior to that based on salt levels for estimating the maximum age of the Earth’s oceans.
E.    None of the salts carried into the Earth’s oceans by rivers are used up by biological activity in the oceans.

答案是A，但是取反之后，想不通是怎么反驳原文的，希望各位牛人能详细帮忙解释一下（最好每个选项都说明一下），不胜感激！！

-- by 会员 梦想守护者 (2010/4/24 13:14:18)

这题我做了，我选的是E ,但答案是A,
文中的推理过程是地球上的rivers 一直把溶解的盐带入海洋中。显然，如果假设一开始海水的盐度为零的话，从现在的盐度可以推算出需要几百年来达到这个盐度。
看A, 如果取反， 就是这几百年来， 进入海洋中的溶解的盐的量比平时来的要大。 我个人认为此不能达到削弱。因为此选项说的是unusually large, 但没有具体说明是和那些年比large 了，，如果要是削弱，那么就是 写 在过去的几百年中，有100 年进入海水的盐分特别高， 比其他的几百年都要高很多，那么就不能从这个推出海洋的年龄。这个选项是把这几百年放在整体一起写的，只是说明这几百年高，而文中也是说的这几百年这段时间，个人认为这个选项只是个事实 ，取反不能削弱。

看E,  如果取反后那么就是 从river 中进入海水的盐 被海洋中的生物活动所用掉了，，那么文中的推理即用过去几百年海水盐度的变化是不可靠的，因为不一定每年用掉的量一样，都是平均的，，所以我觉得这个是削弱，，

求高人解答！

winny莹

顶一个！我也选E

louishirley

我也选E = =|||


A取非其实也说的通。
如果在之前的这么多年里，进入海的盐的数量有几次异常的特别大的波动，unusually larger说明是不同于正常规律，这种异常也许会影响最后的测量。

而且E选项出现了一个biological activity，原文没有提及的词。
即使biological activity会use up salt，这也是个一般规律，一直会发生，不会对测量造成很大的影响。再退一步，如果salt is totally used up by biological activity，那就根本不存在题目描述的可以根据salt来测量age of ocean。

louishirley

补充一下。

E选项，none取非是some。
some salt的变动范围就很大了，如果只是万分之一或者亿分之一的salt被use up，对估计age of ocean是不会造成影响的。