求助逻辑10套练习10和练习8的14题

jocelyna

Pollutants in the atmosphere can cause acid rain
(rain with high acidity levels). While acid rain in
itself cannot significantly affect the acidity of bodies
of water into which it falls, it can greatly increase
the acidity of nearby lakes by increasing the amount
of decaying matter on a forest floor. A recent
increase in the acidity of the water in Forest Lake,
therefore, surely indicates that the rain falling nearby
has become more acid.

    Which of the following, if true, most seriously
    weakens the argument?
    (A) Even in areas without significant amounts  
        of acid rain, most lakes in regions with  
        vegetation similar to the vegetation around  
        Forest Lake have acidity levels higher than  
        those of other lakes.
    (B) Recent air-quality tests in the region around  
        Forest Lake have revealed a slight increase in  
        the amount of pollutants in the air.
    (C) Large-scale logging, which was recently  
        begun in the forest surrounding Forest  
        Lake, has increased the amount of decaying  
        matter on the forest floor.  
    (D) There is some disagreement among scientists  
        about exactly how pollutants in the atmosphere  
        cause acid rain.
    (E) Decaying matter exists on all forest floors  
        and is an important factor in maintaining thehealthy growth of the forests.
我知道可以举出他因,答案选C但是为什么不选A呢？A也说明了vegetation是他因啊？
Neither the Sami nor the Kephrian delegations
attended the international conference. Beforehand. the
delegations of Daqua and Kephria. allies whose
governments had grievances against Tessia. officially
announced that one or both of the two would stay away
if the Tessian delegation attended the conference. In
response, the Sami delegation officially announced that
it would definitely attend if both the Daquan and
Kephrian delegations stayed away.  
If the statements given are all true and all the
delegations adhered to their official announcements.
it must also be true that the
(A) Daquan delegation attended the conference  
(B) Daquan delegation did not attend the conference
(C) Sami government had no grievance against
Tessia
(D) Tessian delegation did not attend the conference
(E) Tessian delegation made no official
announcement regarding its attendance at the
conference
  答案选E,可是我推来推去都觉得是A，请大神赐教,谢谢！

竹林中人

第一个A并不是指出他因，只是说另一个类似的地方的湖水酸性增强了，但没有出现大量的酸雨。vegetation 跟forest floor 意思差不多，不是其他原因

竹林中人

第二个E想不明白

上山帅

第一题很简单，A只是类比，相对于A来，C给出了影响酸度的其他原因，更具说服力。第二题容易陷入误区。其实就是数学里的充分必要条件。结论是S和K都没有attend。给出了条件是D和K这个allies说他们其中一个或者两个都不会attend如果Tattend,并且S说他会attend如果D和K都不参加。你看啊，你是这么推得对吧，因为S没参家，那么S和K都参加了，又S没参加，所以推出D参加了。但你忽视了一个问题，S没参加，有可能的情况是D参加了或者D和S都没参加。从而也不能确定T是否参加。

chenxuqi700

上山帅 发表于 2013-9-2 22:50
第一题很简单，A只是类比，相对于A来，C给出了影响酸度的其他原因，更具说服力。第二题容易陷入误区。其实 ...

你说的不对。其实这题T是混淆的，根本没用。。

直接看最后说：S一定会参加，如果D和K都不参加，现在K事实上是没有参加，S他自己也没有参加，那必然是因为D参加了。如果像你说的D和S都没参加，那不符合S说的“如果D和K都不参加，我就一定参加”

明白了吗？所以这题答案应该是A

chenxuqi700

上山帅 发表于 2013-9-2 22:50
第一题很简单，A只是类比，相对于A来，C给出了影响酸度的其他原因，更具说服力。第二题容易陷入误区。其实 ...

当然E的选项也不错。。也是must be true..就是等于啥也没说了。。