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The Earth s rivers constantly carry dissolved salts into its [#permalink]
 19 Jun 2008, 11:44
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84% (01:18) wrong based on 2 sessions
The Earth’s rivers constantly carry dissolved salts into its oceans. Clearly, therefore, by taking the resulting increase in salt levels in the oceans over the past hundred years and then determining how many centuries of such increases it would have taken the oceans to reach current salt levels from a hypothetical initial salt-free state, the maximum age of the Earth’s oceans can be accurately estimated.
Which of the following is an assumption on which the argument depends?
A. The quantities of dissolved salts deposited by rivers in the Earth’s oceans have not been unusually large during the past hundred years.
B. At any given time, all the Earth’s rivers have about the same salt levels.
C. There are salts that leach into the Earth’s oceans directly from the ocean floor.
D. There is no method superior to that based on salt levels for estimating the maximum age of the Earth’s oceans.
E. None of the salts carried into the Earth’s oceans by rivers are used up by biological activity in the oceans.
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Re: CR: Ocean salinity [#permalink]
19 Jun 2008, 11:57
E for me. Though A is also close but between A and E, I would choose E.
Anyways good questions +1 to you, whats the source?
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Re: CR: Ocean salinity [#permalink]
19 Jun 2008, 13:11
lexis wrote: The Earth’s rivers constantly carry dissolved salts into its oceans. Clearly, therefore, by taking the resulting increase in salt levels in the oceans over the past hundred years and then determining how many centuries of such increases it would have taken the oceans to reach current salt levels from a hypothetical initial salt-free state, the maximum age of the Earth’s oceans can be accurately estimated.
Which of the following is an assumption on which the argument depends?
A. The quantities of dissolved salts deposited by rivers in the Earth’s oceans have not been unusually large during the past hundred years. - So....?
B. At any given time, all the Earth’s rivers have about the same salt levels. - Not a required assumption
C. There are salts that leach into the Earth’s oceans directly from the ocean floor. - Weakens
D. There is no method superior to that based on salt levels for estimating the maximum age of the Earth’s oceans. - We dont care
E. None of the salts carried into the Earth’s oceans by rivers are used up by biological activity in the oceans. E. The assumption is that whatever is carried stays and none is used and hence the correlation can be drawn using the method described. Negate this assumption and we are left with decreasing amounts of salt and hence no correlation can be accurately undertaken.
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Re: CR: Ocean salinity [#permalink]
19 Jun 2008, 13:59
lexis wrote: The Earth’s rivers constantly carry dissolved salts into its oceans. Clearly, therefore, by taking the resulting increase in salt levels in the oceans over the past hundred years and then determining how many centuries of such increases it would have taken the oceans to reach current salt levels from a hypothetical initial salt-free state, the maximum age of the Earth’s oceans can be accurately estimated.
Which of the following is an assumption on which the argument depends?
A. The quantities of dissolved salts deposited by rivers in the Earth’s oceans have not been unusually large during the past hundred years.
B. At any given time, all the Earth’s rivers have about the same salt levels.
C. There are salts that leach into the Earth’s oceans directly from the ocean floor.
D. There is no method superior to that based on salt levels for estimating the maximum age of the Earth’s oceans.
E. None of the salts carried into the Earth’s oceans by rivers are used up by biological activity in the oceans. Consider A, A. The quantities of dissolved salts deposited by rivers in the Earth’s oceans have not been unusually large during the past hundred years. Negate it -> The quantities of dissolved salts deposited by rivers in the Earth’s oceans have been unusually large during the past hundred years. Clearly then our experiment to determine age of the oceans will fail. So, this is an assumption the argument relies upon. IMO - A
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Re: CR: Ocean salinity [#permalink]
19 Jun 2008, 15:31
This has been discussed before. A is my answer. It directly supports the premise. E, could be the answer if A weren't there.
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Re: CR: Ocean salinity [#permalink]
22 Jun 2008, 22:23
We are talking about "quantities of dissolved salts deposited by rivers in the Earth’s oceans" not "salt level of rivers" so B is not correct.
A is OA.
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Re: CR: Ocean salinity [#permalink]
23 Jun 2008, 01:25
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Who wrote this question? The vatican? The ocean is at least 2-3 billions years old, and the question is framing the ocean's salinity age in terms of centuries.
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Re: CR: Ocean salinity [#permalink]
23 Jun 2008, 04:07
lexis wrote: We are talking about "quantities of dissolved salts deposited by rivers in the Earth’s oceans" not "salt level of rivers" so B is not correct.
A is OA. But why is E incorrect ?
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Re: CR: Ocean salinity [#permalink]
23 Jun 2008, 05:33
Hey good one, thank BSD and Anirudh for pointing it out. I guess we normally miss the first option! I fell for E initially.
The method of measurement will hold true only if A is satisfied, ie the incremental measurement is possible only if "The quantities of dissolved salts deposited by rivers in the Earth’s oceans have not been unusually large during the past hundred years" . E is the next best option.
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Re: CR: Ocean salinity [#permalink]
13 Aug 2010, 08:39
Guys, pls help me why B is wrong?
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Re: CR: Ocean salinity [#permalink]
13 Aug 2010, 10:37
I think E is incorrect because the question talks about the increase in Salt level. Thus, the increase in salt level would account for the amount of salt biologically processed.
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Re: CR: Ocean salinity [#permalink]
13 Aug 2010, 11:51
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E is incorrect because the argument is talking about the RESULTING INCREASE, which includes the salts that are used up by biological activity in the oceans or for any other purposes.
B is incorrect because the argument is focusing on the ocean's slat level and not the river's salt level.
Only A remains.
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Re: CR: Ocean salinity [#permalink]
13 Aug 2010, 12:27
seekmba wrote: E is incorrect because the argument is talking about the RESULTING INCREASE, which includes the salts that are used up by biological activity in the oceans or for any other purposes.
B is incorrect because the argument is focusing on the ocean's slat level and not the river's salt level.
Only A remains. I wrongly understood B as river's level of salt was constant (the same) during the all period of time.
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Re: CR: Ocean salinity [#permalink]
14 Aug 2010, 00:52
I was bought by "B" 
Last edited by Financier on 15 Sep 2010, 06:55, edited 1 time in total.
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Re: CR: Ocean salinity [#permalink]
18 Aug 2010, 02:43
A FOR ME
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Re: CR: Ocean salinity [#permalink]
02 Sep 2010, 09:07
I believe E is correct answer
let's consider one thing in the stimulus. it says that we can calculate maximum age of the Earth's oceans, not age alone.
so, even A is true, we can still calculate maximum age of oceans because we still have the data of the salt in the ocean, which originates from rivers. In other words, the amount the rivers carry now in the oceans
but in E, it is very different, if we don't have data from the use of salts from biological activity in the oceans, so we don't know whether the amount rivers carry is all in the ocean. So how we can calculate the MAXIMUM AGE.
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Re: CR: Ocean salinity [#permalink]
02 Sep 2010, 10:57
So then again what is OA? can someone please clarify... Posted from my mobile device 
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Re: CR: Ocean salinity [#permalink]
02 Sep 2010, 12:03
Can someone explain why B and E are wrong?
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Re: CR: Ocean salinity [#permalink]
03 Sep 2010, 00:12
i chose E,, narrowed it down to a & e,
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Re: CR: Ocean salinity [#permalink]
03 Sep 2010, 01:52
Between A and E e seems better.
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Re: CR: Ocean salinity
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03 Sep 2010, 01:52
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