31. Some who favor putting governmental enterprises into private hands suggest that conservation objectives would in general be better served if private environmental groups were put in charge of operating and financing the national park system, which is now run by the government. 结论： national park system由私人掌管->更好！ 削弱：有因无果，由私人掌管不好。
Which of the following, assuming that it is a realistic possibility, argues most strongly against the suggestion above? A. Those seeking to abolish all restrictions on exploiting the natural resources of the parks might join the private environmental groups as members and eventually take over their leadership. （这就是有因无果的一个很好的例子） B. Private environmental groups might not always agree on the best ways to achieve conservation objectives. （不是best，也不一定就是不好啊，像这种一般般的词起不到削弱的作用） C. If they wished to extend the park system, the private environmental groups might have to seek contributions from major donors and general public. （跟私人掌管的方式没有关系啊） D. There might be competition among private environmental groups for control of certain park areas. （competition就一定不好吗？） E. Some endangered species, such as the California condor, might die out despite the best efforts of the private environmental groups, even if those groups are not hampered by insufficient resources.
27. Red blood cells in which the malarial-fever parasite resides are eliminated from a person’s body after 120 days. Because the parasite cannot travel to a new generation of red blood cells, any fever that develops in a person more than 120 days after that person has moved to a malaria-free region is not due to the malarial parasite. Premise: parasite can not travel Conclusion: any, fever, >120 days不是因为malarial parasite 那么削弱就是是因为，有果无因
Which is the following, if true, most seriously weakens the conclusion above? A. The fever caused by the malarial parasite may resemble the fever caused by flu viruses. （无关） B. The anopheles mosquito, which is the principal insect carrier of the malarial parasite, has been eradicated in many parts of the world. （mosquito无关） C. Many malarial symptoms other than the fever, which can be suppressed with anti-malarial medication, can reappear within 120 days after the medication is discontinued. （注意结论的具体性，是说fever，所以other than the fever是错误的） D. In some cases, the parasite that causes malarial fever travels to cells of the spleen, which are less frequently eliminated from a person’s body than are red blood cells. （正确） E. In any region infested with malaria-carrying mosquitoes, there are individuals who appear to be immune to malaria. （无关，没有出现parasite和fever）