The first split I'd go with is the first word of each choice--"either
" versus "cells
." If you look at the non-underlined portion of the sentence, you find the other half of the "either/or" construction -- "or conducted electrical impulses." Ignore the stuff in the middle for the moment to see what the underlying structure is. Which one of the following is parallel?
CELLS SECRETED hormones or
CONDUCTED electrical impulses
SECRETED hormones or
CONDUCTED electrical impulses.
We need the subject (cells) to precede "either" so that we can preserve parallelism. A, B, and C are out.
Both D and E have plural pronouns-- "they" in D and "them" in E. There are several possible plural antecedents for both these words, but don't panic. Pronoun ambiguity is sometimes tolerated on the GMAT, especially when parallelism helps us determine what the writer of the sentence actually means (rendering the pronoun less ambiguous!).
In choice D, the pronoun "they
" is in the SUBJECT case and position--this makes it clear that "they
" is supposed to stand in for "cells
." The meaning of this choice is therefore "CELLS either secreted hormones, in which case CELLS were endocrine cells." This meaning is clear and makes sense.
In choice E, the pronoun "them
" is in the OBJECT case and position. "Them
" should therefore stand in for "hormones
," making the meaning of this choice "cells either secreted hormones
, which made hormones
endocrine cells." (This meaning is reinforced by the use of ", which"--this construction signals a modifier of the noun immediately preceding the comma--here, "hormones"). Choice E doesn't make sense, so it's out.
Remember:If you ever find yourself in a pool of choices that all seem to have ambiguous pronouns, don't panic. A situation that seems like pronoun ambiguity can sometimes be tolerated if the position and case of the pronoun let you figure out the intended antecedent.
Parallelism is a huge structural clue here. (And often, the tolerated almost-ambiguous pronouns tend to be in the subject position).
Hope this helps.
JP Park | Manhattan GMAT Instructor | Los Angeles
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