PT19.S4.Q09 - measurements of the motion of the planet uranus

anupama.satyasai

http://7sage.com/lsat_explanations/lsat-19-section-4-question-09/

While I was solving this, I narrowed the choices to B or D.

B because it provides an alternate explanation for why Uranus is being pulled away;
D because if the Sun exerts less of a pull on Uranus, maybe even the little mass that Neptune and Pluto have can pull Uranus towards them? Hence, an alternative to the existence of another planet.

Please explain to me what the correct thought process for eliminating D is.

Thank you

NYC12345

D is irrelevant. The stimulus is about Uranus being pulled AWAY from the Sun, so the degree of force the Sun exerts on Uranus is irrelevant. Your job is to weaken the claim that there must be another undiscovered planet to account for the gravitational force pulling Uranus away from the Sun. B is the only feasible answer. Does this explanation make sense to you?

nye8870

@anupama.satyasai Right. @alexandergreene93 The argument’s conclusion is that “in addition to the known planets” (as if this argument is going anywhere) there MUST be an additional planet in our solar system. There must be some other “tugging force” pulling Uranus away. The only AC that offers this possible explanation is (B) the belt of comets.