Lead Contamination

This topic has expert replies
Master | Next Rank: 500 Posts
Posts: 113
Joined: Sun May 24, 2009 8:01 am
Thanked: 4 times

Lead Contamination

by italian7745 » Sun Nov 29, 2009 7:58 pm
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.
Source: — Critical Reasoning |

User avatar
Community Manager
Posts: 1537
Joined: Mon Aug 10, 2009 6:10 pm
Thanked: 653 times
Followed by:252 members

by papgust » Sun Nov 29, 2009 10:19 pm
Its B IMO

The stimuli says that major cause of the decline was a 75% drop in the use of leaded gasoline b/w 1975 and 1985.
This choice provides support that most of the decline in discharges of lead occured before 1976, but the largest decline in the level of river contamination occurred between 1980 and 1985.
This means that major cause of the decline was indeed due to drop in the use of leaded gasoline.

Master | Next Rank: 500 Posts
Posts: 171
Joined: Mon Jun 01, 2009 8:59 pm
Thanked: 8 times

by brick2009 » Sun Nov 29, 2009 11:08 pm
was stuck between B and E.

In B: there is a clear demarcation of time line.

Before 76--- MOST of industrial waste decline occured..

between 80-85--largest decline in the level of river contamination occurred => the main reason was drop in used of leaded gasoline.

Legendary Member
Posts: 2326
Joined: Mon Jul 28, 2008 3:54 am
Thanked: 173 times
Followed by:2 members
GMAT Score:710

by gmatmachoman » Mon Nov 30, 2009 2:20 am
italian7745 wrote:
gasoline between 1975 and 1985.
I guess between 1975 and 1985 means both 1975 &1985 are excluded. In that case B holds strong!!

Master | Next Rank: 500 Posts
Posts: 371
Joined: Fri Mar 06, 2009 2:48 am
Thanked: 27 times
GMAT Score:740

by 2010gmat » Mon Nov 30, 2009 2:26 am
B --> clealry tells that decline because of reduced indtl dischge occured before 1976 ... this clear demarcation makes B the best contender..

Master | Next Rank: 500 Posts
Posts: 113
Joined: Sun May 24, 2009 8:01 am
Thanked: 4 times

by italian7745 » Mon Nov 30, 2009 2:52 am
OA is B

Senior | Next Rank: 100 Posts
Posts: 55
Joined: Sun Sep 20, 2009 1:37 pm

by andy123 » Thu Mar 10, 2011 11:12 pm
But can somebody please explain what is wrong with (E)


E -- > also says that it declined in 1985. ?

80% decline due to lead - this is speific.

Legendary Member
Posts: 857
Joined: Wed Aug 25, 2010 1:36 am
Thanked: 56 times
Followed by:15 members

by AIM GMAT » Fri Mar 11, 2011 1:04 am
andy123 wrote:But can somebody please explain what is wrong with (E)


E -- > also says that it declined in 1985. ?

80% decline due to lead - this is speific.
Yep what makes E wrong choice ? i too went with E .
Thanks & Regards,
AIM GMAT

Legendary Member
Posts: 768
Joined: Mon Nov 30, 2009 3:46 am
Thanked: 21 times
Followed by:7 members

by GMATMadeEasy » Fri Mar 11, 2011 1:32 am
What is the source f the question? I find it tricky and ,of course, a good one.

Senior | Next Rank: 100 Posts
Posts: 55
Joined: Sun Sep 20, 2009 1:37 pm

by andy123 » Fri Mar 11, 2011 1:40 am
not sure of the source - was just browsing thru the queries here...

I think the problem is in this statment>> "between 1975 and 1985"

B syas 1976 which is between 1975 and 1985

E says 1985 ... I think 1985 is not considered betwen 1975 and 1985 --- may be this is the reason why E is wrong.