Manhattan Prep Instructor
Joined: 22 Mar 2011
Posts: 2642
Given Kudos: 55
GMAT 2: 780 Q50 V50
Re: Parallelism: What EXACTLY does "and" combine???
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20 Nov 2011, 00:38
This can certainly be a tricky issue. The short answer is that you have to use both meaning and structural cues to decide. Here's my take on your two examples:
1) DIVIDED OVER (whether significant warming will occur) AND (what impact it would have).
It can't be divided over WHETHER (x) AND (y), because "whether . . . and" doesn't make sense. "Whether" indicates a choice between options, while "and" puts things together. Here, the implied choice is "whether or not significant warming will occur," but the "or not" is implied. (It's generally left off as redundant on the GMAT). Otherwise, we'd need "or": WHETHER (significant warming will occur) OR (what impact it would have). Notice that this doesn't make sense either--why would we say that the scientific community is divided over one thing OR the other?
(By the way, some of these GMATPrep problems are seriously outdated--since when is the scientific community divided over whether global warming will occur?)
2) To me, the most logical reading is this:
New hardy varieties of rice show promise of producing high yields without the costly (irrigation and application of commercial fertilizer) that were required by earlier high-yielding varieties.
If this were a stand-alone sentence, you could make a case that costly refers only to irrigation. I'm not sure I'd be convinced, but there wouldn't really be a definitive answer.
New hardy varieties of rice show promise of producing high yields without the ([costly irrigation] and [application of commercial fertilizer]) that were required by earlier high-yielding varieties.
However, since the word "costly" directly precedes either "requirements" or "application" in ALL of the other answer choices, the intended meaning is clearly that both practices are costly.
I hope this helps!