According to the passage, which of the following factors help

The nearly circular orbits of planets in our solar system led scientists to expect that planets around other stars would also reside in circular orbits. However, most known extrasolar planets reside in highly elongated, not circular, orbits. Why? The best clue comes from comets in our solar system. Comets formed in circular orbits but were gravitationally flung into their present-day elliptical orbits when they ventured too close to planets. Astronomers suspect that pairs of planets also engage in this slingshot activity, leaving them in disturbed, elliptical orbits. If two planets form in close orbits, one will be scattered inward (toward its star), the other outward. They will likely then travel close enough to neighboring planets to disturb their orbits also.

According to the passage, which of the following factors help account for the elliptical shape of the orbits of extrasolar planets?

  1. The planets’ formation in close proximity to other planets
  2. The gravitational influence of planets whose original orbits have been disturbed
  3. The gravitational influence of comets

An important thing to keep in mind about the Reading Comprehension section of the GRE as we use PowerPrep online to study is that it is just that—reading comprehension. In other words, as difficult as it may seem, and it can be pretty tricky, the test makers will always give us all the information we need in the passage to answer the question. This is especially true for questions that ask us about particular details of the passage, like question 10 of the second Verbal section on practice test 1.

This question begins with the phrase “according to the passage,” so we know that we need for our answers to be directly supported by information from the passage. Specifically, our question asks for information that helps explain the elliptical shape of the orbits of planets outside of our solar system. Since this is a pretty major idea in the passage, we can use keywords in our answer choices to help us navigate for information if we need to. However, we should still read the passage quickly in order to get an idea of what might explain this phenomenon.

The first sentence of the passage explains that the planets in our solar system move in nearly circular orbits while the second sentence explains that this is not true for other planets. Aha! After the second sentence is the rhetorical question, “why?” which signals that we are about to transition into an explanation of this phenomenon. “The best clue,” the passage explains comes from observing comets, which formed in circular orbits but were flung into elliptical orbits by the gravitational pull of planets they passed. The passage then transfers this reasoning to planets, explaining that planets that form close to each other probably fling each other into an elliptical orbit, which could then affect other planets they get close to.

Alright! So it seems that other planets affect one another’s orbits. Even if we aren’t sure about all of the specifics, let’s keep in mind that we can come back to the passage to test out each answer. Since this is a select-all-that-apply style question, we’ll need to test each answer individually.

  • The planets’ formation in close proximity to other planets

Well we know that the general idea was that planets may affect the orbits of other planets, but if we need to, we can double-check the information towards the end of the passage to see if it says anything about their formation in close proximity to one another being a factor. Aha! The second-to-last sentence specifically states that “if two planets form in close orbits,” or close proximity, “one will be scattered inward and the other outward.” Ok, so it does appear that planets might affect one another’s orbit if they form close together. A is TRUE based on the passage, so we should select this answer.

  • The gravitational influence of planets whose original orbits have been disturbed

Like A, this answer generally sounds correct, but we may want to double-check. Hmm. Yup! The last sentence explicitly states that once planets that have formed close together have their orbits altered by one another “they will likely then travel close enough to neighboring planets to disturb their orbits.” Great! B is also correct based on the passage and should be selected.

  • The gravitational influence of comets

Hmm. The passage did say something about comets. Right after the question “why?” the passage said that the best clue comes from comets, but NOT that comets actually play a role. In the next sentence we’re told that comets are flung into elliptical orbits by planets, but the passage does not state whether or not the reverse is true (it is, however, implied that comets do not affect the orbit of planets since the next sentence is about how scientists predict that planets affect the orbits of other planets). C is not supported by the passage and should not be selected.

As we can see, questions that ask about specific details are really just a test of whether or not we read the passage AND answers carefully. We should not hesitate to go back to the passage for information, but we need to do so quickly and use keywords to help us find information.

 

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