For the last three years, entomologists have been searching for a parasite to help control a whitefly that has recent...

Avi on July 8 at 11:54PM

D vs. E

I struggled between D and E on this one. I had an issue with D because even if you negate it it very well may be that the effort was wasted. For example, if one out of 100 parasites are related to the silverleaf, it is still possible that they didn't find any that helped them at all. E, on the other hand, said that they found a certain parasite for the sweet potato plant. To say that the effort was wasted now isn't true as you did discover something useful.

2 Replies

Shunhe on July 9 at 06:17PM

Hi @avif,

Thanks for the question! So here, we’re dealing with entomologists that have been looking for parasites to help control a whitefly, and in this case they specifically thought it was the sweet-potato whitefly. But turns out it wasn’t, they got it wrong, it’s a silver leaf (or “silverfleaf”) whitefly. So, the argument concludes, the search for a parasite has been wasted effort so far.

Now let’s take a look at (D). And negate it the way you did. Let’s say there is a parasite of the sweet-potato whitefly that’s also a parasite of the silver leaf whitefly. And let’s say it’s 1/100. Well, then it’s not true that the search for a parasite was a wasted effort then! Since it’s not a wasted effort if you made progress, and if (D)’s false, you made progress in identifying one parasite. Then you didn’t waste all your effort so far because of the one parasite, and so the conclusion wouldn’t follow, and negating (D) breaks the argument, so (D) is the correct answer.

(E), on the other hand, is pretty close, but the problem with (E) is that if we negate it, we get that the entomologists found a parasite of the sweet-potato whitefly. But so what? We care about parasites of the silver leaf whitefly. And so (E) doesn’t break the conclusion, since even if (E) is false, then the search for a parasite could still have been wasted effort.

Hope this helps! Feel free to ask any other questions that you might have.

Avi on July 10 at 06:56PM

The issue I have with D is that it doesn't say that they found such a parasite which is a predator for both. It doesn't say that they found any parasite at all. All it says is, that theoretically it could've not been a wasted effort. E, on the other hand, is not a wasted effort because they actually found something useful, albeit, not in the way they were searching.