Q2 - for the last three years

[cvfh17]

why d is better than e? thanks

[tommywallach]

Hey Cvf,

This is a necessary assumption questions, so we'll start by looking at the core (conclusion/premises).

Conclusion: The search for a parasite to control the pest has been wasted effort.

Premise: The entomologists only looked for parasites of the sweet-potato whitefly, but it turns out the pest is a silverleaf whitefly.

There are a number of ways the gap could go here, but the most obvious is that a parasite that affects sweet-potato whiteflies might also affect silverleaf whiteflies.

(A) is a premise booster. We already knew that some varieties were pests; knowing that they're all pests isn't super interesting.

(B) is another premise booster. We already know that a parasite will help to control the pest.

(C) would do the opposite of what we want. This undermines the conclusion, by implying that the search for a parasite might have been useful, even if it was seeking in the wrong direction.

(D) CORRECT. If there's no way that the search for parasites for the sweet-potato whitefly could be applied to the silverleaf whitefly, then the time has been wasted.

(E) is very tricky. This would imply that the search hasn't been successful; it would not, however, imply that the search has been wasted effort. If the same parasites affect both sweet-potato whiteflies and silverleaf whiteflies, then the search has actually been exactly as useful as it could have been. But it may take longer than three years.

Hope that helps!

-t

P.S. Did you notice that, in the passage, they accidentally misspelled silverleaf as silverfleaf? Hee hee.

[mjacob0511]

Tommy:

I'm just confused with how you explained (E). The conclusion was that the search for the parasite has been a wasted effort, and the reason for that is because they were looking for a parasite for the wrong species of whitefly.

Now choice (E) says that the argument has to be assuming that no parasites of the sweet potato whitefly were discovered. However, the effort was not to find parasites for whiteflies, it was to find a parasite for this specific species of whitefly that has become a crop pest. So if you negate the assumption and maybe the entomologists found ten parasites of the sweet potato whitefly, but if none of them are also parasites of the silver(f)leaf whitefly then yes the efforts have been wasted. We don't need or gain anything by discovering parasites of harmless species.

[JosephV]

Tommy:

I'm just confused with how you explained (E). The conclusion was that the search for the parasite has been a wasted effort, and the reason for that is because they were looking for a parasite for the wrong species of whitefly.

Now choice (E) says that the argument has to be assuming that no parasites of the sweet potato whitefly were discovered. However, the effort was not to find parasites for whiteflies, it was to find a parasite for this specific species of whitefly that has become a crop pest. So if you negate the assumption and maybe the entomologists found ten parasites of the sweet potato whitefly, but if none of them are also parasites of the silver(f)leaf whitefly then yes the efforts have been wasted. We don't need or gain anything by discovering parasites of harmless species.

And if one of the ten is a parasite of the silverleaf whitefly?

Then the efforts have not been wasted. You just don't know. It could go either way. The "negation test" (i.e. negating a valid necessary assumption) obliterates the argument with certainty, completely destroys it. As I've shown with the first sentence of this post, this is not the case with answer choice (E).