求教逻辑10套两道题 练习8和练习10的14题

jocelynaUID：3165548

. 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！

jocelynaUID：3165548

求各位大神帮忙看看啦，真心不懂