Answer Choice A is the correct answer because the Passage most clearly discusses “the use of a new astronomical technique,” as can be shown in the opening Paragraph, “The results [...] also show the power of an up-and-coming method of calculating the masses of alien worlds from the way they eclipse their stars,” and the beginning of later Paragraphs which begin with “The new technique,” or “The technique.” Answer Choice B is incorrect because, while the Passage does mention date about certain planets, it focuses more on the technique of TTV than these planets. Answer Choice C is incorrect because no controversial experiment is discussed in the Passage. Answer Choice D is incorrect because, while it might be true that TTV is an innovative procedure, it’s never set in contrast to an already “established procedure,” and so is “easier to disprove” than Answer Choice B.
How to solve this? The Questions asks, “The main purpose of the passage is to [...]?” Because this is a [Big Picture Question], we have to approach this question by (1) having a general understanding of the structure and content of the Passage and (2) looking for particular [high-density information] which can tell us more clearly about the purpose of the Passage. If we track the general purpose of each paragraph, we can outline it in the following way: (1) new exoplanets are found which shows diversity and the power of a new technique, (2) the new technique TTV and what it can do, (3) the origin and idea of the technique, (4) some more history of TTV, (5) when the technique became practical, (6) a finding that used the technique, (7) another finding that used the technique. Looking for particular sentences with [high-density information], we can first look at the title of the Passage, “Star-Crossing Planets Literally Strut Their Stuff.” Because this title doesn’t tell us too much about the content of the Passage we can go down to the introductory paragraph, which ends by stating how new findings “show the power of an up-and-coming method of calculating the masses of alien worlds from the way they eclipse their stars.” The next Paragraph begins with “The new technique,” indicating that the Passage will continue to discuss the technique of TTV. Taking these two together, both the general picture and specific texts, we can say the Passage primarily concerns this new technique of TTV and should expect our answer choice to relate to this.
Answer Choice A says the main purpose of the passage is to “discuss the use of a new astronomical technique.” This does match our understanding of the Passage, so we should keep this option. Answer Choice B says the purpose of the passage is to “provide preliminary data about certain planets.” Based on the opening Paragraph, this might seem plausible. But we should note how the first Paragraph shifts to focus on the technique of TTV and continues exploring it throughout the rest of Passage, so we should eliminate this option. Answer Choice C says the purpose of the passage is to, “argue in favor of a controversial experiment.” Because the Passage doesn’t mention any controversial experiment, we should eliminate this option. Answer Choice D says the purpose of the Passage is to “suggest an innovative alternative to an established scientific procedure.” Although this might seem to plausibly mention TTV as an “innovative alternative,” the Passage never presents it in contrast to an already established procedure, so we should eliminate this option as well. That leaves Answer Choice A, which we should choose as our correct answer.