Sigatoka disease drastically reduces the yield of banana trees and is epidemic throughout the areas of the world wher...

on June 19, 2021

Why not E?

I understand the correct answer, but It seemed to me that E is also necessary. It says "Most of the banana trees that have not been exposed to the Sigatoka fungus grow in small banana groves." If that isn't the case, then most unexposed banana trees would be in large plantations, and there would be no purpose in using the fungicides. So wouldn't E have to be true?

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Victoria on June 19, 2021

Hi @lklop,

Happy to help!

It is true that, if answer choice (E) were not true, then most unexposed banana trees would be in large plantations. However, there are two issues with answer choice (E) based on your logic above. Remember that our conclusion is focused on the effect of the disease on the majority of the world's banana crop.

First, answer choice (E) tells us that most banana trees which have been unexposed to the fungus grow in small banana groves, but we learn nothing about the proportion of unexposed banana trees to exposed banana trees. In this way, even if most unexposed banana trees grew in large plantations, this does not mean that most banana trees are not seriously threatened by the disease.

Second, this does not mean that there would be no purpose in using fungicides. We do not learn any information about the proportion of exposed to unexposed trees and we do not know whether these unexposed trees are immune to the disease or whether they have just not been exposed to it yet. It is entirely possible that 60% of the trees in plantations have been exposed and 40% have not, meaning that it would still make sense to use the fungicide.

There is also one broader flaw with answer choice (E): it does not affect our conclusion. Remember that, for the correct answer, if the assumption is negated then the conclusion can no longer be properly drawn. If we negate answer choice (E), then we learn that most of the bananas that have been exposed grow in small banana groves. This is unfortunate because fungicides cannot be used in small banana groves, but this tells us nothing about the effectiveness of the fungicides and does not address the conclusion which is that most of the world's banana crop is not seriously threatened by the disease.

Hope this helps! Please let us know if you have any further questions.

on June 21, 2021

It does, thanks!