Critical Reasoning

Agricultural societies cannot exist without staple crops. Several food plants, such as kola and okra, are known to have been domesticated in western Africa, but they are all supplemental, not staple, foods. All the recorded staple crops grown in western Africa were introduced from elsewhere, beginning, at some unknown date, with rice and yams. Therefore, discovering when rice and yams were introduced into western Africa would establish the earliest date at which agricultural societies could have arisen there. Which of the following is an assumption on which the argument depends?

A. People in western Africa did not develop staple crops that they stopped cultivating once rice and yams were introduced.
B. There are no plants native to western Africa that, if domesticated, could serve as staple food crops.
C. Rice and yams were grown as staple crops by the earliest agricultural societies outside of western Africa.
D. Kola and okra are better suited to growing conditions in western Africa than domesticated rice and yams are.
E. Kola and okra were domesticated in western Africa before rice and yams were introduced there.

[spoiler]OA: Will be posted later. Please discuss each answer choice in detail.[/spoiler]

Answer : A

Answer : A

A. People in western Africa did not develop staple crops that they stopped cultivating once rice and yams were introduced. - tricky option-might act as the correct answer but here we are contradicting something stating in the stem which is inappropriate- the info in the stem cannot be directly reversed.- i am not sure about this one :/

B. There are no plants native to western Africa that, if domesticated, could serve as staple food crops. correct answer-negate this and this option will weaken the main conclusion- "many native WA plants can actually be staple crops- thus the arguement conclusion is contradicted"


C. Rice and yams were grown as staple crops by the earliest agricultural societies outside of western Africa. - already stated in the stem


D. Kola and okra are better suited to growing conditions in western Africa than domesticated rice and yams are. - out of scope- Kola and okra stuff is the premise here and not the conclusion

E. Kola and okra were domesticated in western Africa before rice and yams were introduced there.- even if they were domesticated they are not staple crops so who cares ???

i hope that the answer is A

B is attractive but to me it fails to mention that people must also cultivate or process this crops
to provide living.for example there is no great benefit of wheat, if people simply don`t know what plant is it, or how to process it into food.
on the contrary if people cultivate staple crops, but then stoped doing so in favor of rice then the exact appearing of societies does not match with that of rice

Yes it has to be A

Negate A:
People in western Africa did develop staple crops that they stopped cultivating once rice and yams were introduced [ removed Not]

Now observe the word "All" in the below premise.
"All the recorded staple crops grown in western Africa were introduced from elsewhere". Negated A has definite hit on this line.

As per powerscore these are a kind that are rare in GMAT. I still beleive killing premise is like destroying...

hspa,,,thats exactly why I went wit B, cause A is killing the premise and not the conclusion.

while B would actually kill the conclusion "discovering when rice and yams were introduced into western Africa would establish the earliest date",,,,since there were other natives already present before this introduction...

IMO B

B

what is the level of this one ??'

bblast wrote:hspa,,,thats exactly why I went wit B, cause A is killing the premise and not the conclusion.

while B would actually kill the conclusion "discovering when rice and yams were introduced into western Africa would establish the earliest date",,,,since there were other natives already present before this introduction...

I re-read the powerscore. It says that assumption can fill the gap btw two premises. It seems that only for weaken questions we cannot kill the premise. Hmmm... wasnt easy to comprehend.

However I am still not with B because even on negating B I found it has no effect on conclusion.
Negated B: There are plants in africa that can serve as staple food crops but conclusion is about determining period of introduction to rice in africa
Staple crop has no impact in determining period... Let go B