请教一道题 谢谢大家啦！！GWD-13-31

joyous314

By competing with rodents for seeds, black ants help control rodent populations that pose a public health risk.  However, a very aggressive species of blank ant, the Loma ant, which has recently invaded a certain region, has a venomous sting that is often fatal to humans.  Therefore, the planned introduction into that region of ant flies, which prey on Loma ants, would benefit public health.
Which of the following, if true, most strengthens the argument?
A.    Ant flies do not attack black ants other than Loma ants.
B.    Loma ants are less effective than many bird species in competing with rodents for seeds.
C.    Certain other species of black ants are more effective than Loma ants in competing with rodents for seeds.
D.    The sting of Loma ants can also be fatal to rodents.
E.    The use of pesticides to control Loma ants could have harmful effects on the environment.
答案选A 是排除了其他的才选择它的 原来上逻辑课的时候老师说没有正确的选项，只有最好的选项
可是我还是想把A搞明白...为神马捏...谢谢大家了！！

sdcar2010

Well, if A is right, then the ant flies would ONLY  attack the aggressive Loma ants without affect the GOOD black ants who help control rodents. If not, the ant flies might help the rodents to eat seeds by removing the rodents' predator - black ants.

joyous314

厄...突然明白了，原来是没有仔细读题干的细节啊，我又傻了..==谢谢楼上！

1006002952

那为啥不选D啊，那样也可以控制rodent啊

sdcar2010

那为啥不选D啊，那样也可以控制rodent啊

-- by 会员 1006002952 (2011/6/12 20:29:54)

Pay attention to main conclusion, which is: the introduction of ant flies would benefit human health.

If D) is right, the human are still in danger (once stung by the L-ant). So D) alone would not support the conclusion.