9. (D)
Question Type: Assumption
This argument is tricky. The conclusion made by the naturalist is that recent claims that the tiger is not extinct are false. In other words, his/her conclusion is that the tiger is indeed extinct. The evidence presented is that the tiger’s natural habitat was taken over by sheep farming, and that naturalists have no evidence of the tiger’s existence in the region. But, isn’t the author assuming that the tiger hasn’t moved to another region? Answer (D) expresses this assumption. Notice that when the assumption is explicitly stated, it helps to support the argument ("We can’t find evidence of the tiger here, and they haven’t moved somewhere else, so they no longer exist."), and that this assumption is absolutely necessary in order for the conclusion to be drawn.
(A) is tempting because it would support the argument. However, the author doesn’t need to assume that the tiger became extinct because of starvation.
(B) actually weakens the argument. If scavengers can destroy tiger carcasses, this may explain why naturalists haven’t been able to find evidence of the tiger’s existence (a reason other than extinction). This can’t be a necessary assumption if it goes against the argument.
(C) is tempting, but the author doesn’t necessarily need to assume that every naturalist has looked systematically for the tiger.
(E) is not a necessary assumption either. The author already states that the sightings are alleged sightings, so it is not necessary to assume that those who have reported sightings are inexperienced.
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