Because dinosaurs were reptiles, scientists once assumed that, like all reptiles alive today, dinosaurs were cold-blooded. ███ ██████ █████████ ██ ████████ ███████ ██ ███ ████████ ███████ ████████ ███ ███ █ ██████ ██ ███████████ ██ ████████ ████ ██ █████ ████ █████████ █████ ████ ████ █████████████ █████ ███████████ █████ ███ ████ ████ ████████████ ███████ █████ ████ █████████ ███ ██████ ████████████ ████ ███ ██████████████ ██ ██████ ████████ ███████ ████████████ ███████ █████ ████ ██████ ██ █████ ██ ███ ███████ █████
The researchers hypothesize that at least some dinosaurs may have been warm-blooded. Why do they think so? Because dinosaur fossils were recently found in the northern arctic. And only warm-blooded animals could have survived the cold of arctic winters; cold-blooded animals would have frozen to death.
Because this argument follows a phenomenon-hypothesis pattern, we can weaken by suggesting a competing hypothesis to explain the observations. For example, maybe the temperatures in the arctic were much warmer during the time of the dinosaurs. Whatever the specific answer, it will tell us how dinosaurs could have lived in the northern arctic without being warm-blooded.
Which one of the following, ██ █████ ███████ ███ ██████████████ █████████
Today’s reptiles are █████████ ████████ ██ ███████ ██ █████████ ██ ████ ████████ █████████
The stimulus
The fossils show ███ ██████ █████████ ██ ████ ████ █████████████ ███████ ████ █████ █████ ███████ ██ ██████████
Does the size of an animal correspond to its likelihood of being warm- or cold-blooded? We don't know, so this information isn't relevant to the scientists' argument. Without more details, the relative size of the arctic dinosaurs doesn't weaken the hypothesis.
The arctic dinosaur ███████ ████ █████ █████████ ███████ ██ ██████ █████ ███ █████ ███████ ██ █████████ █████████ ████ █████████████
If anything, (C) strengthens the argument by undermining a competing hypothesis that the arctic was warmer when these dinosaurs lived. If the arctic dinosaurs coexisted with cold-resistant plants, that suggests that the arctic was still cold at that time. That only makes it more likely that the dinosaurs had to be warm-blooded.
The number of ███████ █████ ████████ █████████ █████ ██ █████████ ██ █████ ████ ████ █████ ████ ██ ███████ ██ ████ █ █████████ ████ ███████
So the kind of dinosaurs that lived in the northern arctic were likely migratory. This suggests an alternative explanation for why the dinosaurs were found in the arctic: they migrated through that region, but didn't stay there year-round. And if the dinosaurs migrated south for the winter, they wouldn't need to survive the arctic cold, undermining the hypothesis that they were warm-blooded.
Experts on prehistoric ████████ ██████████ ███████ ████ ██████ ████████████ ██ ███ ███████████ ████████ ██████ ████ ███ █████████████ █████████ ████ ████ ████ ███ ██████
Like (C), (E) undermines a competing hypothesis of climate change, although it does so more directly. Doing so only affirms the researchers' assumption that the arctic winter was still very cold when the dinosaurs lived, and thus strengthens the argument.
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