GMAT grammar question subject (verb agreement)

[Mngirl]

This is a sentence correction problem from my GMAT review:

The direction in which the Earth and the other solid planets - Mercury, Venus, and Mars - spins were determined from collision with giant celestial bodies in the early history of the solar system.

(A) spins were determined from
(B) spins were determined because of
(C) spins was determined through
(D) spin was determined by
(E) spin was determined as a result of

The answer is D. How do I determine which verb is supposed to agree with which subject? Why can't spin relate to direction? Is there a rule that I should learn?

thank you,
MNGirl

[Yankee]

Hi mngirl

First of all, a direction doesn't spin. Try looking at the sentence this way:

The direction was determined by ...

The direction [that the earth spins] was determined by ...
.

[Mngirl]

I see. Thank you!