问问逆否命题

Lucky0506

Nature constantly adjusts the atmospheric carbon level. An increase in the level causes the atmosphere to hold more heat, which causes more water to evaporate from the oceans, which causes increased rain. Rain washes some carbon from the air into the oceans, where it eventually becomes part of the seabed. A decrease in atmosphere carbon causes decreased evaporation from the oceans, which cause less rain, and thus less carbon is washed into the oceans. Yet some environmentalists worry that burning fossil fuels may raise atmospheric carbon to a dangerous level. It is true that a sustained increase would threaten human life. But the environmentalists should relax---nature will continually adjust the carbon level.

132. Each of the following can be inferred from the information in the passage EXCEPT:

A.        A decrease in the level of atmospheric heat causes a decrease in the amount of carbon that rain washes into the oceans from the air.

B.        An increase in the level of carbon in the atmosphere causes increased evaporation of ocean water.

C.        An increase in the level of atmospheric heat causes increased rainfall.

D.       A decrease in the level of carbon in the atmosphere causes decreased evaporation of ocean water.

E.        A decrease in the level of atmospheric heat causes a decrease in the level of carbon in the atmosphere.

Reference:

1。On the one hand:

An increase in the level of carbon-〉 more heat-〉 more water to evaporate from the oceans-〉 increased rain-〉 washes more carbon from the air into the oceans-〉 becomes part of the seabed

2。On the other hand:

A decrease in atmosphere carbon-〉less heat-〉decreased evaporation from the oceans-〉less rain-〉 washes less carbon from the air into the oceans

Hence, it is obvious that the correct answer is E

我想问问，题目中的什么条件可以退出A decrease in atmosphere carbon-〉less heat ？

我觉得如果从An increase in the level of carbon-〉 more heat来推，其逆否命题不是：

less heat->decrease level of carbon吗？

好晕啊~~  请大家多多指教！

[此贴子已经被作者于2005-7-20 9:02:58编辑过]

eggfriedrice006

I find it easier to follow this train of thought:



A: If there's a decrease in the atmosphere carbon

B: then there's less heat

If A, then B, as given in the argument



Answer (E) puts the logic backward: If B, then A; which does not always work, thus it's the answer.  



Hope this helps

Lucky0506

Thanks for your response.  However, my confusion is about how could we get :

以下是引用eggfriedrice006在2005-7-20 13:29:00的发言：
I find it easier to follow this train of thought:


A: If there's a decrease in the atmosphere carbon

B: then there's less heat

If A, then B, as given in the argument

Isn't that from the passage, we only get:

A: If there's a increase in the atmosphere carbon

B: then there's more heat

If A, then B, as given in the argument

Please help clarify the difference.  Many thanks!

eggfriedrice006

You are absolutely right.  But in this case, there are 2 parallel
logic tracks going on at the same time as you referred to above:


1。On the one hand:

An increase in the level of carbon-〉 more heat-〉
more water to evaporate from the oceans-〉 increased rain-〉 washes more
carbon from the air into the oceans-〉 becomes part of the seabed

2。On the other hand:

A decrease in atmosphere carbon-〉less heat-〉decreased evaporation from the oceans-〉less rain-〉 washes less carbon from the air into the oceans



Answers A - D can all be worked out through this logic, however, Answer E stands out.  Here's my perspective on why:



Look at logic track #2 - If there's a decrease in the atmosphere carbon
level, then there's less heat; this sets up the If A, then B.
Answer E attempts to prove the reverse (If B, then A): If there's less
heat, then there's a decrease in the carbon in the atmosphere.



If A then B does not guarantee if B then A.  Thus, Answer E is the choice.  



I hope this helped explain.  

Lucky0506

谢谢蛋炒饭~！  

我想，我可能没有说清楚我的问题。

我就是不明白，原文的那一句话可以推出：

A decrease in atmosphere carbon-〉less heat

我觉得原文根本就没有以上的逻辑链条。有的仅仅是

A decrease in atmosphere carbon-〉decreased evaporation from the oceans

你可以告诉我原文中的什么信息，或者从哪一句话可以得到：

A decrease in atmosphere carbon-〉less heat吗？

非常感谢！