At the end of 1997 several nations stated that their oil reserves had not changed since the end of 1996. But oil res...

Mehran on August 1, 2016

@csdinkel let's break it down.

The conclusion here is, "So most of the nations stating that their oil reserves were unchanged are probably incorrect."

And the support provided for this conclusion is:

P1: "At the end of 1997 several nations stated that their oil reserves had not changed since the end of 1996."

P2: "But oil reserves gradually drop as old oil fields are drained and rise suddenly as new oil fields are discovered."

SC: "Therefore, oil reserves are unlikely to remain unchanged from one year to the next."

The question stem here is asking us to identify "an assumption the argument requires" so this is a Strengthen with Necessary Premise question.

We are looking for the answer choice that not only strengthens this argument but that is also necessary for the argument.

Notice that there is a major gap in this argument from P2 to the subsidiary conclusion (SC).

What if a country neither drained existing old fields nor found new oil fields in the same year? Then it would be possible that the country's oil reserves remain unchanged.

(B) states, "It is likely that in 1997, in most of the nations that stated that their oil reserves were unchanged, old oil fields were drained or new old fields were discovered, or both."

So most of these nations either drained old fields, discovered new fields or did both in 1997.

This strengthens the argument by ruling out the possibility I set forth above, i.e. that a country neither drained existing old fields nor found new old fields.

Now let's negate (B) to make sure that it is also necessary to this argument.

The negation of (B) is "It is NOT likely that in 1997, in most of the nations that stated that their oil reserves were unchanged, old oil fields were drained or new old fields were discovered, or both."

The negation means that it is likely that most nations referenced neither drained old oil fields nor discovered new fields, which destroys the conclusion that "most of the nations stating that their oil reserves were unchanged are probably incorrect."

So (B) would be the correct answer choice here.

Hope this helps! Please let us know if you would like us to discuss any of the other answer choices here.

amiru77 on October 24, 2017

Hi,
Thanks for the explanation. I picked A and only when I reviewed the questions and negated this answer choice found out that this choice was not a necessary assumption for the argument. I have two questions on this: 1- Is this choice sufficient for justifying the argument? I mean could it be correct choice if the Q stem asked for a strengthen with sufficient?
2- Could you please confirm my negated version of answer choice A:
For SOME nation with oil reserves, it is NOT more likely that the nation was mistaken in its statements about changes in its oil reserves than that the nation's oil reserves remained unchanged.
Thanks

amf on April 13, 2020

Hi could you please explain why A would be incorrect?