Thanks Mike for the detailed explanation.
I would have answered this question had the question been Explain the paradox; The paradox being that despite controlled atmosphere, students found the difference in growth rates. And the answer Choice D would be apparent.
But, for Evaluate the argument, I usually apply "Variance Analysis" i.e testing the extremes and then analyzing the behavior of the argument.
d. Heavy vehicular traffic such as is found in cities constantly deposits grime on greenhouse windows, reducing the amount of light that reaches the plants inside
Applying variance analysis:
Lets say that Yes. heavy vehicular traffic deposited grime on greenhouses windows, and reduced the light. -> It could be a possible factor in the difference of the growth rates of the plants.
However, if you say that there is no such grime deposited on greenhouse gases, and possibly the amount of light is same in greenhouses, then it is not describing the behavior of the growth rates.
Here, I am getting confused, if it is not the cause of difference in growth rates, then what could possibly be the factor behind the growth rates.
Another doubt is that I have seen evaluate questions comes in two varieties -
First is in which the answer choices starts with "Whether, Would , Were" etc that converts it into a form of question. In such questions, I can easily apply variance analysis.
However, second categories have plain answer choices such as the answer choices in this question.. then is it correct to apply Variance analysis here, or what should be the appropriate strategy.
I'm happy to respond.
To be perfectly honest, forget "variance analysis". Forget any pre-fab, one-size-fits-all rule. The GMAT excels at creating diverse questions ---- each new questions depends on a logical twist unique to that particular situation and unlike anything in any other question. if you try to apply fixed rules to the GMAT CR, it will fool you time and time again. You must forget all general methods, and dive into a critical analysis of what is unique and particular about the individual situation at hand.
In Evaluate the Argument questions, a correct answer need only have impact on the argument if the question is answered one way. Suppose there's a GMAT CR argument, and it's a "evaluate the argument" prompt. Suppose the OA is: "Whether P causes Q
?" Now, suppose that, if P does cause Q, that would significantly change the argument, but if P does not cause Q, that would have zero effect on the argument. That's perfectly fine. That's the norm for Evaluate the Argument CR questions. The OA may pose a question that has crucial implications for the prompt argument either way, but that's not necessary ---- as long as one way of answering that question has crucial implications for the argument, then it doesn't matter whether the other answer would not affect the argument at all.
Does all this make sense?
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