hazelnut 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 ocean to reach current salt levels from a hypothetical initial salt-free state, the maximum age of the Earth's oceans can be accurately estimate.
Which of the following is the 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.
GMATNinja & GMATNinjaTwo (A), (B) and (E) are pretty close to each other. How to eliminate the incorrect answer choices?
As for choice (B), we don't care about the relative salt levels in the individual rivers, only about the cumulative amount of salt carried into the oceans. It doesn't matter if some rivers carry more salt than others.
As for choice (E), "taking the resulting increase in salt levels in the oceans over the past hundred years" will tell us how much the salt levels increased DESPITE loss of salt due to biological activity (or any other factor that would reduce salt levels in the ocean). If the impact of these factors is small, these factors will not significantly affect the calculations. In other words, it is okay if A SMALL AMOUNT of salt is used up by biological activity in the oceans.
This thread contains several other posts explaining (B) and (E), so please review these before posting additional questions.
i think your reason for eliminating E is saying -- this sentence "taking the resulting increase in salt levels in the oceans over the past hundred years" could account / could already incorporate for loss of salt due to biological activity (or any other factor that would reduce sea salt levels in the ocean)
as a test taker -- how would one figure out if this sentence ["taking the resulting increase in salt levels in the oceans over the past hundred years"] could / could not account for this ?
Its quite possible that the sentence ["taking the resulting increase in salt levels in the oceans over the past hundred years"] has not thought about this possibility [ i.e. the loss of salt due to biological activity (or any other factor that would reduce sea salt levels in the ocean)
04 Feb 2020, 14:19
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