[求助]逻辑解题中“有果无因”。。。不理解 请高手指教

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

怎么个有果无因削弱？

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。

怎么个有因无果？

我觉得这几个都是同一个道理，可我没太搞懂，希望有人可以指教 谢谢了！

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.

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.

B. The anopheles mosquito, which is the principal insect carrier of the malarial parasite, has been eradicated in many parts of the world.

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.

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. 
            D

E. In any region infested with malaria-carrying mosquitoes, there are individuals who appear to be immune to malaria.

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.

B. Private environmental groups might not always agree on the best ways to achieve conservation objectives.

C. If they wished to extend the park system, the private environmental groups might have to seek contributions from major donors and general public.

D. There might be competition among private environmental groups for control of certain park areas. 
                A

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题似乎不是无因有果。

无因有果：

原文说A→B，

削弱：在没有A的情况下也有B（说明不是A导致了B）。

27题，是寻找他因

原文假设红细胞是virus的唯一宿主，所以红细胞被清除以后的fever就与virus无关

D选项，说明红细胞不是唯一宿主，还有别的宿主。

谢谢，能不能把1.有因无果2因果颠倒3因果关系的资料不准确 这几个方面的例子列一下啊