Quote:
A) the buildings in Mesopotamian cities, which were arranged haphazardly, the same basic plan was followed for all cities of the Indus Valley: with houses
The word "unlike" is the first thing that should leap off the page at us. This is begging you for a nice, strict comparison. (And if you aren't 100% comfortable with comparisons, check out
this video or
this sequel.)
But the comparison doesn't work in (A): "Unlike
the buildings in Mesopotamian cities...
the same basic plan was followed for all cities of the Indus Valley..." Nope, we can't really compare "buildings" to a "plan."
There's another minor problem, though. In general, colons are used to introduce examples or descriptions or definitions, and in this sentence, the colon introduces a more detailed description of "the basic plan". But there's really no reason to use the preposition "with" in front of that description. (And the really good news is that the nuances of colon or semicolon or dash usage are rarely tested on the GMAT. More on GMAT punctuation in
this video.)
For what it's worth: I'm OK with the idea that "which were arranged haphazardly" could modify the entire phrase "buildings in Mesopotamian cities", and not the cities themselves. But the comparison error alone is definitely enough to disqualify (A).
Quote:
B) the buildings in Mesopotamian cities, which were haphazard in arrangement, the same basic plan was used in all cities of the Indus Valley: houses were
(B) has exactly the same comparison error as (A): "Unlike
the buildings in Mesopotamian cities...
the same basic plan was used in all cities of the Indus Valley..." Nope, we still can't really compare "buildings" to a "plan."
I'm also not crazy about the phrase "which were haphazard in arrangement" -- it's a pretty inelegant way to say "which were arranged haphazardly." But I'm not certain that it's definitely WRONG. And I'm much more comfortable with the description after the colon, for whatever it's worth -- see the explanation for answer choice (A) for more on this issue.
Anyway, the comparison error is about as bad as it gets, so (B) is gone.
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C) the arrangement of buildings in Mesopotamian cities, which were haphazard, the cities of the Indus Valley all followed the same basic plan: houses
(C) rearranges a bunch of stuff, but the comparison is still a mess: "Unlike
the arrangement of buildings in Mesopotamian cities...
the cities of the Indus Valley..." Nope, we can't compare "the arrangement" to "the cities."
There's also a little bit of a problem with the modifier "which were haphazard". Because "were" is plural, the sentence seems to be saying that either the cities or the buildings themselves were haphazard, and neither of those make sense: the arrangement was actually haphazard.
So we have two strong reasons to cross out (C).
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D) Mesopotamian cities, in which buildings were arranged haphazardly, the cities of the Indus Valley all followed the same basic plan: houses were
Hurray, the comparison is acceptable now. "Unlike Mesopotamian cities... the cities of the Indus Valley..." Yup, that's cool.
And I don't see any other potential issues. The "which" modifier is clear as a bell now: "in which buildings were arranged haphazardly" clearly describes "Mesopotamian cities." The phrase after the colon is a perfectly reasonable description of the "basic plan."
Let's keep (D).
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E) Mesopotamian cities, which had buildings that were arranged haphazardly, the same basic plan was used for all cities in the Indus Valley: houses that were
And once again, the comparison is crap: "Unlike Mesopotamian cities... the same basic plan..." Nope.
And there are some other minor issues. The modifier "which had buildings that were arranged haphazardly" isn't WRONG, exactly, but it's a messy and wordy way to say "in which buildings were arranged haphazardly." Plus, the chunk after the colon is no longer parallel: "
houses that were laid out on a... grid, and
houses and walls were built of standard-size bricks." That's not OK: the noun phrase "houses that were laid out" is not parallel to the clause "houses and walls were built..."
So (E) is gone, and we're left with (D).