Question Statistics:
38% CHOOSE: whose interiors were inhumanely overcrowded, their floors often serving as beds, and their walls often windowless and dilapidated with age and neglect
42% CHOOSE: whose interiors were inhumanely overcrowded, their floors were often serving as beds, and their walls were often lacking windows and dilapidated due to age and neglect
4% CHOOSE: whose interiors were inhumanely overcrowded, their floors were often serving as beds, and they had walls often windowless and dilapidated with age and neglect
8% CHOOSE: having interiors inhumanely overcrowded, their floors often serving for beds, and their walls were often windowless and dilapidated due to age and neglect
8% CHOOSE: having interiors that were inhumanely overcrowded, their floors often serving as beds, and their walls often lacked windows and were dilapidated on account of age and neglect
Sample size = 4,707
Read the Original Sentence Carefully, Looking for Errors:
Though this sentence is long and not necessarily in your favorite style, there is nothing grammatically wrong with it.
Stripped way down, the last part of this sentence would read: "The interiors were overcrowded, their floors serving as beds, and their walls windowless." The last two clauses are descriptive clauses, parallel to each other but not to the first phrase.
It may seem odd, but here the word "serving" in the phrase "their floors often serving as beds" actually functions as an adjective. This is fairly common, however. For example, in the sentence "She ran for the bus, shouting, and finally caught it" the verbs "ran" and "caught" are parallel, while the word "shouting" functions as an adjective, describing what she was like while "she ran for the bus."
In the case of this sentence, "their floors often serving as beds" describes the extent to which the "interiors were inhumanely overcrowded." Similarly, the phrase "their walls often windowless and dilapidated..." is a descriptive phrase. It helps explain exactly how "inhumanely overcrowded" the apartments were.
Since there is nothing actually wrong with this sentence, we'll just check each choice to see if any of them is better stylistically.
Scan and Group the Answer Choices:
There is a clear and useful 3-2 split here. Choices (A), (B) and (C) all begin "whose interiors were" and choices (D) and (E) both begin with "having interiors."
Eliminate Wrong Answer Choices:
Choices (D) and (E) both begin with the word "having," which is incorrect, because if we write simply "having" it isn't clear who or what has these interiors. Is it the apartments, the immigrants, or Jacob Riis? Such ambiguity is unacceptable, which is enough reason to rule out these two choices. Further, (D) changes "dilapidated with age" to "dilapidated due to age," and (E) changes it to "dilapidated on account of age." Neither of these changes is preferable to the original "with." In fact, the phrase "on account of" is usually wrong on the GMAT. So, both choices (D) and (E) are incorrect.
Choice (B) makes several small changes from choice (A). First, it changes "floors often serving" to "floors were often serving." This small change has big implications. Without the word "were," the phrase "their floors often serving as beds" was a descriptive aside. With "were," this is an independent clause (it could stand on its own) so it would at the very least have to be parallel with the first clause. However, it isn't parallel; to be parallel, it would have to read, "whose floors served as beds." Choice (B) also inserts the word "were" in the last clause, which creates exactly the same problem there. Finally, it unnecessarily changes the phrase "dilapidated with" to "dilapidated due to." "With" is fine, so there's no reason to make the phrase any longer. Because of these problems, choice (B) is wrong.
Since each of the other choices introduces new errors, the sentence is correct as written and Answer Choice (A) is correct.
Remember, you shouldn't automatically assume that all "-ing" verbs are wrong. It's true that they are not stylistically preferred, but there are certain circumstances in which they are correct. This sentence illustrates one particular way in which the testmaker can and does use "-ing" verbs - as a present participle that sets off a descriptive clause. Also, in long sentences with many commas, take the time to make sure you know what is supposed to be parallel to what.
