Answer Choices C and D are the correct answers because Lines 49-53 say, “Bottke and Levison’s computer simulations show that the observed number of objects is about right if they are immigrants, though they have assumed many of the objects broke up after transport.” These Lines tell us most clearly that the two scientists base their conclusions on the assumption that a lot of the objects that made it to the asteroid belt broke up after migrating. If this assumption weren’t true, it would weaken their argument. This matches Answer Choice C from Question 26 which says that the scientists’ conclusion would be weakened by a study that “demonstrated that very few objects broke up after migrating to the asteroid belt.” For Question 27, Answer Choice A is incorrect because these Lines only explain what these two scientists studied and don’t offer any suggestion of what would weaken their study. Answer Choice B is incorrect because these Lines also only explain what the scientists focused on in their study, without saying any assumption they based their findings on or any of their reasoning, making it hard to find something that would weaken their study. Answer Choice C is incorrect because these Lines also mostly give facts about what the scientists focused on and because it doesn’t match any of the answer choices for Question 26. For Question 26, Answer Choice A is incorrect because Bottke and Levison’s conclusion depends on the fact that the Sun burned away the outermost layer of some objects, so this would support their conclusions. Answer Choice B is incorrect because Bottke and Levison’s conclusions don’t depend on the stability of objects in the inner solar system. Answer Choice D is incorrect because their conclusions doesn’t depend on immigrants from the outer solar system surviving in the asteroid belt, and actually suggest the opposite, that they “broke up” after transport.