PrepTest 116

Incorrect. Based on Statement #2, we can conclude that vegetables grown without fertilizer were grown in soil that was not completely depleted of nutrients, so this answer choice is contradicted by the stimulus.

Incorrect. The soil that the vegetables were grown in wasn't completely devoid of nutrients, which either means the crops were rotated or other preventive measures were taken. That leaves open the possibility that crops were rotated, though, so this answer is incorrect.

Correct. Argument or Facts:
Facts

Question Type:
Must Be True

Stimulus Summary:
(1) not Preventative measure taken → Failure to rotate crops causes soil depletion
(2) Soil completely depleted AND not Fertilizer applied → not Further crops grown
(3) All other things equal AND Vegetables grown in fertilized soil → More vulnerable to pests → Treated with pesticides
(4) The more pesticides used, the more health risk to humans
(5) (Stem) Some vegetables are grown in unfertilized soil

Answer Anticipation:
It's important to note in this question that the stem itself provides information about what we're going to need to make an inference about—vegetables grown in soil that has never had fertilizer applied.

With that in mind, we should head up to the stimulus to find which ones speak to such vegetables. And in that stimulus, there are two sets" of statements. The first set (statements #1 and #2) talk about growing crops, and the second set (statements #3 and #4) are about pesticide and risk to humans.

For the first set, #1 doesn't speak about vegetables, so we can skip over that. Statement #2, however, does—it talks about further crops being grown. In this case, we know that crops were grown—we've got vegetables in unfertilized soil. So let's take the contrapositive of the statement in order to see what must be true:
Further crops grown → not Soil completely depleted OR Fertilizer applied

The sufficient condition there is triggered, allowing us to conclude that either the soil wasn't completely depleted, or that fertilizer had been applied. However, since the question stem asks us about vegetables grown in soil that had never had fertilizer applied, the other option in the necessary condition must be true—that the soil was not completely depleted. That's one potential answer.

For the second set of statements, it can be easy to dismiss #3 because it talks about vegetables grown in fertilized soil. However, the outcome of that is comparative—these vegetables are more vulnerable to pests than vegetables grown in unfertilized soil. So since the statement is comparative, based on statements #3 and #4, we can infer about vegetables from unfertilized soil that (all other things equal) they'll be less vulnerable to pests, use less pesticide, and present less of a health risk to humans. Another potential answer!

Let's head to the answer choices to see which of these shows up.

Answer Explanation:
Based on Statement #2, we anticipated this as a potential answer—at least the first half. The second half is supported as well (we already went through this in answer choice (B)). The soil that the vegetables were grown in wasn't completely devoid of nutrients, which either means the crops were rotated or other preventive measures were taken. That leaves open the possibility that crops were not rotated, justifying the second half of this answer.

Key Takeaway:
Don't gloss over the question stem! It sometimes has more information than just the question type in it, and missing out on that piece can really throw a wrench in the works.

Incorrect. The discussion of pesticides was relative—vegetables grown in unfertilized soil require less pesticide, and thus pose a lower risk. That leaves room for there to be some risk from pesticides from vegetables grown in unfertilized soil.

Incorrect. First, this answer seems to imply that these vegetables weren't treated with pesticides, which isn't justified (see the explanation for (D)). Second, pesticide treatment increases health risk to humans, so this answer has the risk reversed.