Critical Reasoning

ansumania wrote:oops ..my bad...I wanted to know why E can't be correct. .......

kevincanspain wrote:The argument claims that by examining a time sample of the last one hundred years, we can estimate the age of the oceans. Yet how do we know that the last 100 years were representative of the history of the earth in terms of salt deposits in the oceans? Likewise, how do we know that the transactions in your bank account in the past 6 months are representative of the past decade?

DanaJ wrote:Received a PM.

I guess it's clear why A is a good choice: we cannot draw any conclusions on history unless we know for sure it's been the same.

However, I too initially thought E was a reasonable option. But there's a problem: if you take the increase in the past hundred years, this increase has occurred WHILE animals were in the water processing salts. So the increase in the past hundred years is basically a net amount of salt, equal to the amount of salt brought in by the rivers MINUS what's being used up by the animals. This increase in the past hundred years is therefore reliable, since it also takes into account what animals take up. This is why E can't be the answer choice: even if some animals were using salts, then it really doesn't matter.

DanaJ wrote:Yes, you are right about E.

A is the argument of consistency: if you do not have a consistent flow of salt for the past millions of years, then you cannot draw any conclusions based on the amounts for the past hundred years.

ssgmatter 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

I chose E which makes the most sense because it has to be assumed that the salt level is not used for any other purpose so as to measure the age of the Earth

Am I correct??..

Please share your thoughts guys

Thanks!