Happy to help. The question asks us to select the answer that best describes the organization of the passage. For this type of question, it helps to predict the answer by thinking to yourself how each paragraph functions in the passage.
We know the first paragraph outlines an old, popular hypothesis for explaining species diversity. The second paragraph provides support that casts doubt on this hypothesis. The third paragraph outlines a new hypothesis, and the fourth paragraph says that this new hypothesis is probably right.
Now that we've got a general summary of the structure of the passage, let's look at the answer choices.
Answer A says, "a hypothesis is discussed, evidence that undercuts that hypothesis is presented, and a new hypothesis that may account for the evidence is described." This answer choice accurately captures the structure of the passage and each of its paragraphs, and it paraphrases the outline we've made above. This is the correct answer choice.
Answer B is incorrect because it starts out with "a recently observed phenomenon is described," and we know that the first paragraph is dealing with an old belief. This answer is out.
Answer C is incorrect because it starts with "several hypotheses," but there are only two hypotheses discussed in-depth in this passage. This answer is out.
Answer D is incorrect because the second part of the answer says "and evidence provided to suggest that the hypothesis is only partially correct." We know this is false, as the author rejects the old hypothesis in favor of the new one.
Answer E is incorrect because it mentions experiments designed to test each theory, but there is no discussion about experiments in the passage, so we know this answer can be eliminated.
Does this make sense? Let us know if you have any more questions!
