Explain answer choices

Sure! In the first paragraph, the author lays out the traditional theory, that species use a method of play fighting that is more or less the same for each instance. The Galapagos tortoise is an example of one such species' behavior. A is wrong because we have no idea how many species use this display, and the traditional theory doesn't tell us anything about the number of species that use each kind of display. B is wrong because the author never tells us that some but not all species use this, and that is not how the tortoise example plays into the passage. C is wrong because this doesn't serve as evidence for such a claim but rather, it illustrates what the theory in general is talking about. D is wrong because we don't know that it's unique to the tortoise E is correct since it's an example that illustrates the traditional theory.