Ina certain wildlife park, park rangers are able to track the movements of manyrhinoceroses because those animals wear radio collars. When, as often happens, a collar slips off,it is put back on. Putting a collar on arhinoceros involves immobilizing the animal by shooting it with a tranquilizerdart. Female rhinoceroses that have beenfrequently recollared have significantly lower fertility rates than uncollaredfemales. Probably, therefore, somesubstance in the tranquilizer inhibits fertility.
Inevaluating the argument, it would be most useful to determine which of thefollowing?
A. Whether there are more collaredfemale rhinoceroses than uncollared female rhinoceroses in the park
B. How the tranquilizer that is used forimmobilizing rhinoceroses differs, if at all, from tranquilizers used inworking with other large mammals
C. How often park rangers need to usetranquilizer darts to immobilize rhinoceroses for reasons other than attachingradio collars
D. Whether male rhinoceroses in the wildlife parklose their collars any more often than the park’s female rhinoceroses do
E. Whether radio collars are the only practical means that park rangershave for tracking the movements of rhinoceroses in the park
The premises: 1) Tranquilizer used during recollarization: Recollared --> tranquilizer used
2) Recollared females have low fertility. Recollared --> low fertility
The conclusion: some substance in the tranquilizer inhibits fertility: tranquilizer used --> low fertility
For this argument to hold, the assumption is that NOTHING other than the tranquilizer can cause low fertility.
C is the answer since
1) If further evidence shows that never-recollared females who have been tranquilized also have low fertility, then the argument is strengthened.
2) If futher evidence shows that never-recollared females who have been tranquilized do NOT have low fertility, then the argument is weakened.
If we know that the tranquilizer is never used other than collarizing rhinos, the argument is valid.
However, if we know that the tranquilizer is used in other situations on female rhinos, plus the info from the stimulus that these affected female rhinos do not have low fertility rate, then the argument that the tranquilizer causes low fertility in female rhinos will be in trouble.
Therefore, whether tranquilizer is used in other situations is an important information to have for the evaluation of the argument.
As to the strenthening or weakening aspect, you have to look at the conclusion, which links the tranquilizer to low fertility. If new findings add more weight behind the conclusion, it's a strengthener. If new finidings cast doubt on the conclusion, it's a weakener.作者: bobdog179 时间: 2012-4-26 06:32
感谢作者: socool1990 时间: 2012-4-26 21:30
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