Self-study
Biologist: Support Lions and tigers are so similar to each other anatomically that their skeletons are virtually indistinguishable. ███ █████ █████████ ███ █████ ██ ██ █████ ██████████ ██████ ████ ████ ██ ████████ ████████████ ███████ █████ ████ ██ ██████ █████ ███████████████ ██████ ██████████ █████ ██████ ██ ███ █████ ██ ████████ ███████ ████ ███████ █████████ ████████ ████ ██ ███████ ██████████ ██████ ██ ██████
Summary
The biologist concludes that paleontologists can’t infer that extinct predators, like some dinosaurs, hunted in packs just based on their skeletons. He supports this by pointing out that, even though they have very similar skeletons, tigers hunt alone, while lions hunt in packs.
Missing Connection
The biologist concludes that you can’t make a certain inference about extinct predators simply because you can’t make the same inference about lions and tigers. However, he never connects lions’ and tigers’ hunting behavior and skeletons with extinct predators’ hunting behavior and skeletons.
To get from his premises to his conclusion, the biologist must assume, at minimum, that if you can’t infer lions’ and tigers’ hunting behavior based only on their skeletons, then you also can’t infer extinct predators’ hunting behavior based only on their skeletons.
20.
The conclusion is properly drawn ██ █████ ███ ██ ███ █████████ ██ ████████
a
The skeletons of █████ ███ ██████ ███ ██ █████ ████████ ███████ ██ █████████ ██ ███████ ███ ████████ ██ ███ █████████ ██ ██ █████ ████ ███████ █████████ ████████
Too weak. The biologist does fail to show how extinct predators are relevantly similar to lions and tigers. But (A) is much too weak to guarantee the conclusion that paleontologists can’t infer extinct predators’ hunting behavior based only on their skeletons.
b
There have existed ██ █████ ███ ███████ ██ ███████ █████████ █████████ ████ ████ ██ ███████ ██ ████ █████ ████ █████ ████████ ███████ ██ █████████ ██████████████████
It’s possible that all pack-hunting predatory dinosaurs had similar skeletons but that they’re different from the skeletons of those who hunted alone. (B) doesn’t give us enough information to guarantee that one can’t infer extinct predators’ hunting behavior from skeletons alone.
c
If skeletal anatomy █████ ██ ████ ██ ██████████ █████ ███ █████████ █ ██████████ ████████ ███████ █████████ ████ ██ ██ █████ ██████████ ██ ██████ █████ ██ ████████ ███████ ██████ ████ █ ███████ ██ ███████ ██████ ██ ██████
We know that skeletal anatomy alone is an inadequate basis for inferring the hunting behavior of lions and tigers. So (C) guarantees that it is never reasonable to infer hunting behavior based on skeletal anatomy alone. This satisfies the “at minimum” assumption described above.
d
If any two ██████ ███████ ████ █████████ █████████████████ ████████ ███████ ███████ █████ █████████ ███████ ██████████ ████ ██ ██ █████ ██████████ ██ ██████ █████ ██████ ██ ███ ███████ ████████ ██ █████ ████████ ████ ███ ███ ███████ ████ ███ ████ ████████ ████████
Instead, we need an answer choice that establishes that if two animal species with similar skeletons exhibit different hunting behaviors, then it’s never reasonable to infer, based solely on their skeletons, the hunting behavior of any other species.
e
If it is ████████████ ██ ██████ ██████ ██ ███ █████ ██ ███████████ ██ ████████ ████████ ████ ███████ ███████ ██ ███ ████████ ███████ ████████ ██ █████ ███████ █████████ ████ ███ ████████ ███████ ██ █████ ███ ███████ ███ █████████ ██████████████████
We’re trying to prove that it is unreasonable to infer, solely on the basis of skeletal anatomy, the hunting behavior of extinct predators. (E) just tells us that this is only true if the skeletal remains of two species are virtually indistinguishable.