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The level of lead contamination in United States rivers [#permalink]
 19 Sep 2005, 19:48
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The level of lead contamination in United States rivers declined between 1975 and 1985. Federal regulations requiring a drop in industrial discharges of lead went into effect in 1975, but the major cause of the decline was a 75 percent drop in the use of leaded gasoline between 1975 and 1985.
Which of the following, if true, best supports the claim that the major cause of the decline in the level of lead contamination in United States rives was the decline in the use of leaded gasoline?
(A) The level of lead contamination in United States rivers fell sharply in both 1975 and 1983.
(B) Most of the decline in industrial discharges of lead occurred before 1976, but the largest decline in the level of river contamination occurred between 1980 and 1985.
(C) Levels of lead contamination in rivers fell sharply in 1975-1976 and rose very slightly over the next nine years.
(D) Levels of lead contamination rose in those rivers where there was reduced river flow due to drought.
(E) Although the use of leaded gasoline declined 75 percent between 1975 and 1985, 80 percent of the decline took place in 1985.
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Re: CR - Lead contamination [#permalink]
20 Sep 2005, 04:42
rahulraao wrote: The level of lead contamination in United States rivers declined between 1975 and 1985. Federal regulations requiring a drop in industrial discharges of lead went into effect in 1975, but the major cause of the decline was a 75 percent drop in the use of leaded gasoline between 1975 and 1985.
Which of the following, if true, best supports the claim that the major cause of the decline in the level of lead contamination in United States rives was the decline in the use of leaded gasoline?
(A) The level of lead contamination in United States rivers fell sharply in both 1975 and 1983.
(B) Most of the decline in industrial discharges of lead occurred before 1976, but the largest decline in the level of river contamination occurred between 1980 and 1985.
(C) Levels of lead contamination in rivers fell sharply in 1975-1976 and rose very slightly over the next nine years.
(D) Levels of lead contamination rose in those rivers where there was reduced river flow due to drought.
(E) Although the use of leaded gasoline declined 75 percent between 1975 and 1985, 80 percent of the decline took place in 1985.
Realy arbit choices.
A- Gives no proper indication that contamination was less due to leaded gasoline.
B- Might be correct, if we assume that there can be only 2 reasons for decline of contamination.
C- Wrong.
D- Wrong.
E- The fact that use of leaded gasoline declined by 75% could mean that the contamination level in US rivers is decreased.
so, B or E...
I will go with B...
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Re: CR - Lead contamination [#permalink]
20 Sep 2005, 04:45
rahulraao wrote: The level of lead contamination in United States rivers declined between 1975 and 1985. Federal regulations requiring a drop in industrial discharges of lead went into effect in 1975, but the major cause of the decline was a 75 percent drop in the use of leaded gasoline between 1975 and 1985.
Which of the following, if true, best supports the claim that the major cause of the decline in the level of lead contamination in United States rives was the decline in the use of leaded gasoline?
(A) The level of lead contamination in United States rivers fell sharply in both 1975 and 1983.
(B) Most of the decline in industrial discharges of lead occurred before 1976, but the largest decline in the level of river contamination occurred between 1980 and 1985.
(C) Levels of lead contamination in rivers fell sharply in 1975-1976 and rose very slightly over the next nine years.
(D) Levels of lead contamination rose in those rivers where there was reduced river flow due to drought.
(E) Although the use of leaded gasoline declined 75 percent between 1975 and 1985, 80 percent of the decline took place in 1985.
Realy arbit choices.
A- Gives no proper indication that contamination was less due to leaded gasoline.
B- Might be correct, if we assume that there can be only 2 reasons for decline of contamination.
C- Wrong.
D- Wrong.
E- The fact that use of leaded gasoline declined by 75% could mean that the contamination level in US rivers is decreased (Decrease happened in 1985 : We possibly need some time before this could have some impact on river contamination level)
so, B or E...
I will go with B...
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Senior Manager
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2 postings by mistake. Plz see the second one.
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It would be B instead of E, under this logic.
The number of cars using unleaded increased over time. Older cars using leaded gasoline decreased over time. Hence the supply of lead for contamination was decreasing – at an increasing rate. This is a a geometrically decreasing slope curve.
In terms of only the information provided in this question - The only way that a “shockâ€
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between E and B too
I would have chosen E naturally but now I have doubts...  ...this one is not easy
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IMO it is E
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I think B here.
It says MOST of the decline of industrial discharge occured before 1976 (when the regulation was inacted) BUT that the MAJORITY of the decline in river contamination occured between 1980 and 1985.
The decline caused by the law would've occured before this...assuming that the companies all complied with the regulation right away.
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Director
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IMO B
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Director
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Well, the OA is B!
But still not sure why its B and not E! 
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rahulraao wrote: Well, the OA is B! But still not sure why its B and not E! Rahul, acc. to E, the major decline in leaded gas usage occurred in 1985,but we know that the levels decreased between 1975 and '85, not just in '85.
B offers better validation, since it correlates the drop in leaded gas usage and drop in lead contamination levels, at the same time, showing clearly that the drop in contamination is not due to the new federal regulations of '75.
Does that make things any clearer?
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Thanks Anand! ITs much clear now. guess the key word here is BETWEEN!
That would eliminate E!
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Man that was a tough one.
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