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I don't understand why C is incorrect here and E is correct.

Thanks

danget bobby wrote:I don't understand why C is incorrect here and E is correct.

Thanks

The argument notes that if and only if *one* of the effects makes a substantial contribution, will that mutation be favored in natural selection.

(C) doesn't contradict this -- a species might have a trait that reduces survival potential. This has nothing to do with being favored in natural selection. For the record, even if it was favored, that might still be okay -- the argument allows for the possibility of negative traits being favored, as long as they're carried along with a trait that is really positive.

(E) is impossible -- the argument clearly states that if and only if there is trait that makes a substantial contribution will that mutation be favored. If all the traits are neutral, then it doesn't meet the condition of having at least one making a substantial contribution. As per the question stem, this could not be true. ('could be true, except')

(C) UNSC --> increased int'l peacekeeping <--some--> against increased refugee spending
(E) increased role <--some--> UNSC <--|--> southern hemisphere

The problem with C is best illustrated with a simple example:
5 countries with seats on the UN Security council
8 countries in favor of increased int'l peacekeeping
2 countries against increased refugee spending

Without more information, we can't say for sure that the first and third groups overlap. In choice E, on the other hand, the some overlap leads to a direct negative inference about the southern hemisphere. Some countries in favor of a greater role have seats on the UN Security Council, and none of the countries with seats on the UN Security Council are in the southern hemisphere.