Tough GMATprep question - Can any experts help answer?

[kaps786]

Hi Experts - This is a GMATprep question and I cant seem to understand it though I have read a previous post on this before with some explanations. Can someone help.

To me, this seems to be an like an identify the assumption question

Please do explain your approach. Thanks,


Urban air contains more sulfur dioxide than does rural air, and plants in cities typically grow more slowly than do plants in rural areas. In an experiment to see how much of the difference in growth is due to sulfur dioxide, classes in an urban and a rural school grew plants in greenhouses at their schools and filtered the greenhouse air to eliminate sulfur dioxide. Plants in the urban greenhouse grew more slowly than those in the rural greenhouse. Which of the following, if true, would it be most important to take into account in evaluating the result?

A. The urban school was located in a part of the city in which levels of sulfur dioxide in the air were usually far lower than is typical for urban areas.
B. At both schools, the plants in the greenhouses grew much more quickly than did plants planted outdoors in plots near the greenhouses.
The urban class conducting the experiment was larger than the rural class conducting the experiment.
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.
E. Because of the higher levels of sulfur dioxide in the air at the urban school, the air filters for the urban school's greenhouse were changed more frequently than were those at the rural school.

[confuse mind]

IMO - D

[GMATGuruNY]

Urban air contains more sulfur dioxide than does rural air, and plants in cities typically grow more slowly than do plants in rural areas. In an experiment to see how much of the difference in growth is due to sulfur dioxide, classes in an urban and a rural school grew plants in greenhouses at their schools and filtered the greenhouse air to eliminate sulfur dioxide. Plants in the urban greenhouse grew more slowly than those in the rural greenhouse.

Which of the following, if true, would it be most important to take into account in evaluating the result?

A. The urban school was located in a part of the city in which levels of sulfur dioxide in the air were usually far lower than is typical for urban areas.
B. At both schools, the plants in the greenhouses grew much more quickly than did plants planted outdoors in plots near the greenhouses.
C. The urban class conducting the experiment was larger than the rural class conducting the experiment.
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.
E. Because of the higher levels of sulfur dioxide in the air at the urban school, the air filters for the urban school's greenhouse were changed more frequently than were those at the rural school.

The two greenhouses were SIMILAR in one respect: each was filtered to eliminate sulfur dioxide.
Yet the plants in the urban greenhouse grew more slowly than those in the rural greenhouse.
Why?
To evaluate the result, we need to know whether there were any DIFFERENCES between the two greenhouses.

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.
This answer choice offers a key DIFFERENCE between the two greenhouses: since the urban greenhouse was covered with grime, the plants inside received less light than those contained in the rural greenhouse.

The correct answer is D.

Reasons to eliminate the other answer choices:

A: Irrelevant, since each greenhouse was filtered to ELIMINATE sulfur dioxide.

B: This answer choice offers a SIMILARITY between the two greenhouses.

C: The size of each class is irrelevant.

E: This answer choice merely confirms that the urban greenhouse more than likely eliminated sulfur dioxide from the internal air.

[agarwalva]

I guess kaps786 is right.. this looks like assumption
Its is little tough for me too


->

p1: Urban air contains more sulfur dioxide than does rural air
p2; plants in cities typically grow more slowly than do plants in rural areas


Expermient conducted to find much of the difference in growth is due to sulfur dioxide:- an urban and a rural school grew plants in greenhouses at their respective schools and filtered the greenhouse air to eliminate sulfur dioxide

result of expermient - growth is diff between the two green houses


What is asked - what of the following is important to Evaluate the result (to reach a conlusion)

Possible Conclusion
1. s02 is a factor
2. So2 is not a factor

but the important underlying asumption is "there is no other factors between the two enviornments"

Ans D points at this

Mitch Hunt do you think my reasoning is right

[heymayank08]

Urban air contains more sulfur dioxide than does rural air, and plants in cities typically grow more slowly than do plants in rural areas. In an experiment to see how much of the difference in growth is due to sulfur dioxide, classes in an urban and a rural school grew plants in greenhouses at their schools and filtered the greenhouse air to eliminate sulfur dioxide. Plants in the urban greenhouse grew more slowly than those in the rural greenhouse.

Which of the following, if true, would it be most important to take into account in evaluating the result?

A. The urban school was located in a part of the city in which levels of sulfur dioxide in the air were usually far lower than is typical for urban areas.
B. At both schools, the plants in the greenhouses grew much more quickly than did plants planted outdoors in plots near the greenhouses.
C. The urban class conducting the experiment was larger than the rural class conducting the experiment.
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.
E. Because of the higher levels of sulfur dioxide in the air at the urban school, the air filters for the urban school's greenhouse were changed more frequently than were those at the rural school.

The two greenhouses were SIMILAR in one respect: each was filtered to eliminate sulfur dioxide.
Yet the plants in the urban greenhouse grew more slowly than those in the rural greenhouse.
Why?
To evaluate the result, we need to know whether there were any DIFFERENCES between the two greenhouses.

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.
This answer choice offers a key DIFFERENCE between the two greenhouses: since the urban greenhouse was covered with grime, the plants inside received less light than those contained in the rural greenhouse.

The correct answer is D.

Reasons to eliminate the other answer choices:

A: Irrelevant, since each greenhouse was filtered to ELIMINATE sulfur dioxide.

B: This answer choice offers a SIMILARITY between the two greenhouses.

C: The size of each class is irrelevant.

E: This answer choice merely confirms that the urban greenhouse more than likely eliminated sulfur dioxide from the internal air.

mitch,
i think that the option D aren't we assuming too much..i mean the argument never says about light or does light has any effect on the growth of plant??
While in option B it says that the plant in city grew more fast than its neighbouring plants, form which we can obviously conclude that due to sulphur dioxide the neighbouring plants were not able to grow as fast as the plants in the green house were.
Am i going wrong somewhere??pls explain

[hariharan3112]

The Question here is since even when the SO2 was removed from each of the sites, the plants at the urban site still kept growing slow..which means there is some other reason why the plants were actually growing slow..and hence this reason is shown in (D)

[heymayank08]

The Question here is since even when the SO2 was removed from each of the sites, the plants at the urban site still kept growing slow..which means there is some other reason why the plants were actually growing slow..and hence this reason is shown in (D)

option B says just the opposite that the plants didn't grow slowly..

but option B says that the plants in cities didnt grew slow, instead it says that the plants grew faster than the plants nearby..i.e. where the SO2 level was more,...

[ihatemaths]

evidence1.: U(s)>R(s) and U(p)< R(p) U=Urban;R=Rural;s=Sulphur;p=Plants
evidence2:plants in urban green house took longer time to grow , than their rural counterparts.

possible assumption:
is there is some kind of connect between the URBAN AIR , levels of pollution and how they affected the growth. so

D seems perfect

[metallicafan]

+1 D