gmatdriller wrote:Hi Mike@magoosh,
Please what do you think would determine the best answer if C and D
were:
c. all the other planets, all contributing according to their
d. all the other planets, each contributing according to its
i.e "all....their" Vs "each...its"
That's a great question,
gmatdriller. I'm happy to answer.
Let's go back to the original sentence with correct answer (D)
In his experiments with gravity, Isaac Newton showed how the motion of each planet in the solar system results from the combined gravitational pull of the Sun and all the other planets, each contributing according to its mass and distance from others.
You propose an alternate to (C):
In his experiments with gravity, Isaac Newton showed how the motion of each planet in the solar system results from the combined gravitational pull of the Sun and all the other planets, all contributing according to their mass and distance from others.
Yes, now we have agreement between "all" and "their", so that's no longer a problem. One problem that remains is: "their" refers to all the planets, but "mass and distance" are singular. Not all th planets have the same mass. Each has a unique mass. Therefore, we would need those words in the plural.
In his experiments with gravity, Isaac Newton showed how the motion of each planet in the solar system results from the combined gravitational pull of the Sun and all the other planets, all contributing according to their masses and distances from others.
This version is technically grammatically correct, insofar as all the singulars & plurals match up correctly. The problem is more subtle, about the logic of the sentence. We want to emphasize the complexity of Newton's model --- the motion of any one planet depends on the Sun's gravity and on the gravity from each other planet. Say we are looking at Mars and its orbit --- the Sun's gravity has one impact, Earth's gravity on Mars has another impact, Jupiter's gravity on Mars has yet another impact, etc. etc. The orbit of Mars depends on all the different impacts. Each planet has a unique impact on each other planet: that is the nature of the complexity of the Newtonian model.
The construction "each contributing according to its" captures the particularity of the interactions, whereas "all contributing according to their" lumps everything together in way that might obscure the full complexity. Therefore, the "each" version is better than the "all" version. BTW, this final distinction is, in all likelihood, more subtle that the GMAT SC would address.
Does that make sense? Let me know if you have any further questions.
Mike
