Astronomer: In most cases in which

Answer choices

1. A

   No Impact8% picked this

   When two planets or other large objects in orbit have a close encounter, usually the smaller of the two

   This answer is describing what would happen if two planets had a close encounter, but we're trying to find an answer that makes us more likely to think that two planets had a close encounter. This isn't ruling out an alternate explanation for the oval orbits, nor is it giving us any additional plausibility for the author's explanation. If we had more data to pair with this (i.e. if we knew, in these distant solar systems, that the smaller of the two planets who we think had a close encounter was the more affected one, then this answer would be adding some plausibility to the close encounter hypothesis).

   8%
2. B

   Mixed Impact7% picked this

   There is no indication that the orbit of any planet orbiting our sun has been affected by a close encounter with

   For the sake of the 4 or so planets that have circular orbits around the Sun, this answer would strengthen. A lot of plausibility-strengtheners take the form of "where cause is absent, the effect is absent" (or No Cause No Effect for short). Since our author thinks that Cause Effect Close encounter w/ other planet Oval orbit She would be thinking that in situations where planets did not have close encounters with other planets, they would not be likely to have oval orbits. This answer is telling us that no planet in our solar system had close encounters w/ a planet, so if all the planets in our solar system were non-ovals, this would be a decent strengthener. But we were only told that Earth and several (~3) other planets are circular. So the other four are probably ovals, just like most of the planets we observe distantly. If Neptune and Uranus have oval orbits, but no planet in our solar system has ever had a close encounter with another planet in this solar system, then this answer would actually Weaken the argument. So because of its mixed / unclear impact, it's kind of a wash.

   7%
3. C

   Correct55% picked this

   In most cases in which planets have been discovered orbiting a distant star, more than one planet has

   Why this is right

   This very weakly strengthens the plausibility of the author's hypothesis by establishing a Necessary Assumption of that hypothesis. Consider the counterfactual --- if it weren't the case that for most of these planets we observe in the distance, we see more than one planet orbiting that star, that would mean that most of the time we see these planets (with their oval orbits), these planets are the only planet orbiting their star. That would destroy the author's hypothesis. These planets can't be getting their oval orbits via close encounters with another planet orbiting the same star if there are NO other planets orbiting the same star! So the author definitely needs to assume that there is more than one planet orbiting a star in these solar systems, for her hypothesis to work. Establishing that there are multiple planets in these solar systems is a very weak strengthener, but it adds some plausibility.

   Skill tested: Strengthen · how this choice captures the argument's function is the move to repeat next time.

   55%
4. D

   Unrelated to Goal: comets22% picked this

   Most comets with an oval orbit around our sun were thrown into that orbit by a close encounter

   We're only concerned with planets here. We're interested in hearing about Alternate Explanations for how these distant planets got oval orbits, and this answer is not referring to any alternate storyline for the planets' oval orbits. Or we're interested in making the author's story seem more plausible, and this answer has nothing to do with helping to persuade us that these distant planets had close encounters with other planets in their same solar system.

   22%
5. E

   Weakens8% picked this

   For each distant star that has been found to have a planet, no other object large enough to affect the planet's orbit

   This annihilates the plausibility of the author's hypothesis. There's no way these oval orbits were caused by a planetary close encounter if, according to this answer, there are no other objects large enough to affect that planet's orbit.

   8%