Please look at the question below

Unlike smaller apertment buildings, which have fewer than four residential units in them, each room within any residential complex must be equipped with a sprinkler system.
(A) Unlike smaller apartment buildings, which have fewer than four residential units in them
(B) Apert from those apartments that are in buildings that contain fewer than four residential units
(C) In contrast to smaller apartment buildings that contain fewer than four residential units
(D) Unless the apartment building contains fewer than four residential units
(E) Excluding those apartment buidlings that have fewer than four residential units in them


Answer (D)
Time to weed out the misplaced modifiers. The beginning of the nonunderined portion of the sentence begins with each room, so if the sentence wants to compare anything by using the word Unlike, the underlined portion should also be about rooms. (A) compares smaller buildings to rooms, and so do (B) and (C), even though they replace Unlike with Apart from and In contrast to, respectively. A lemon painted blue is still a lemon. (E) survives the first cut because it doesn't commit this error, although its construction is still awkward because it suggests that each room is Excluding those apartment buildings. Given the choice of (D) or (E), though, (D) is much more concise.

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I don't really understand the answer's explaination. Can someone explain it to me better? Thanks.

Unlike/"Apart from"/"In Contrast to" are comparators. These all have been put up as lemons/colored(blue) lemons in the explanation.
Since we need a conditional rather than comparator, we settle for D.
E says that all the apartment building having less than 3 residential units will have sprinkler system, whereas question talks about sprinkler within same building.


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