Several Tyrannosaurus rex skeletons found in North America contain tooth marks that only a large carnivore could have...

AndreaK on December 31, 2019

Hi @tomgbean,

Good question. This stem is asking us which one of the following is most strongly supported. I actually think this is one of the trickiest question types, because it doesn't go so far as to mean must be true. Therefore, the right answer might require some assumptions. But again, we're not trying to prove that something MUST be true, so that's okay...instead, we are trying to identify which scenario from the answer choices is most supported by the limited evidence we are given in the stimulus. So, you're going to want to look for an answer choice that lines up with as much of the information given in the stimulus as possible, because that's what we are basing our reasoning on to say an answer choice is "most strongly supported."

Let's consider the information we're given in the stimulus here. The tooth marks are so that only a large carnivore could have made them, and T. rex was the only large carnivore around at the time. The marks could only have resulted from one of two encounters: combat or feeding. However, such tooth marks would have been impossible to inflict on a living animal.

The last line is the key here. We are given one of two options to explain the tooth marks: combat or feeding. Assuming an animal engaging in combat is alive during that, the last line rules out option 1, combat. So, since we have teeth marks that still need explaining, and one of our two options has been ruled out...the evidence strongly supports that the teethmarks came from option 2, feeding.

A) not relevant, we don't really have any premises that support this idea
B) relevant, but it goes too far....we don't have evidence to support that it was common for carnivores to do this. We just have evidence that support the idea that sometimes (with unspecified frequency) carnivores did this. Maybe T. rexes prefer fresher fair than other dead T. rexes...I guess when you're at the top of the food chain, you get to be a little picky! But what if food is in short supply? Maybe only then do they go after others of their own kind. But, we can't prove it was "common" with the evidence we have here.
C) Bingo! My explanation for B should clarify why C is correct. The "sometimes" here is very key.
D) It's most strongly supported that the dinosaur was feeding. We can't really come to any conclusions about what combat was like for them with this specific set of evidence.
E) We're given no information about what was living on other continents. With no evidence to support this at all, this answer choice is out quickly!

Hope this helps! Feel free to follow up with any other questions you may have.