QUESTION TEXT: All known deposits of the mineral tanzanite…
QUESTION TYPE: Parallel Reasoning
CONCLUSION: Ashley is unlikely to collect a stone that didn’t originate in Tanzania.
REASONING: All known deposits of Tanzanite are from Tanzania.
ANALYSIS: This is a good argument. It’s possible we’ll discover Tanzanite outside Tanzania. But the argument is appropriately cautious: it’s only “unlikely” that Ashley will get a rock from outside Tanzania.
All of the answer choices use the same terms: frogs, owls, lagoon, and island. So pay very close attention to the relationship between those terms, and choose the one that is as uncertain as the stimulus.
- This is a bad argument. The lagoon has many frogs, but there might also be many frogs outside the lagoon but still on the island.
- This is a bad argument. The frogs are only eaten by the owls. But this doesn’t say that the owls only eat frogs from the island. The owls could eat frogs from other islands.
- Frogs are the only animals to live in the lagoon but that doesn’t mean that all frogs live in the lagoon. The owls could therefore eat frogs that live outside the lagoon.
- CORRECT. All frogs live in the lagoon, as far as we know. If owls eat only frogs then they’ll only eat animals from the lagoon unless we discover frogs that live outside the lagoon.
- This is a good argument, but it’s more strongly worded than the stimulus. The stimulus said all known deposits of Tanzanite are on the island. Answer choice D said that all known frogs live in the lagoon. This answer is too certain: it says that every frog (known and unknown) does live in the lagoon.
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