PT106.S1.Q8 > Analytics

Hide analysis

Generally speaking, if the same crop is sown in a field for several successive years, growth in the later years is poorer than growth in the earlier years, since nitrogen in the soil becomes depleted. ████ ██████ ███████ ██ █ ███████████████ █████ ███ ████ █████████ ███ ██████ ██ ████████ ██ ███ █████ █████████████ ██ ████ ██ ███████ ██ ███ ████ █████ ████ █████ █████ █████ ████ ████ ██ ███ █████ █████ ████ ██ ████ ██ ███ ███████ ██████

Structure: Surprising Phenomenon

The stimulus tells us about a surprising phenomenon. Generally, when the same crop is sown in a field for several years in a row, there will be a decreasing yield from that crop because the nitrogen levels in the soil become depleted. Alfalfa is a plant that fixes nitrogen: i.e., it increases, not decreases, the amount of nitrogen in the field. The phenomenon we want to explain is why alfalfa still grows less well in later years than earlier ones if it is planted in the same field several years in a row.

Which one of the following, ██ █████ ████ █████ ██ ███████ ███ ██████████ █████████ █████ ███████ ███████ ███ ███████████████████ ███████

Question Type

Resolve reconcile or explain

We want to explain why alfalfa, like non-nitrogen-fixing plants, grows less well in a field if it is planted several years in a row, even though alfalfa increases the amount of nitrogen in a field instead of decreasing it. The reason this phenomenon is surprising is because we were just told that in general, the reason crops grow less well in the same field over several years is that nitrogen becomes depleted.

But just because nitrogen depletion is one cause of poor crop growth doesn't mean there aren't other causes for poor growth. For instance, maybe too much nitrogen in the soil can also be harmful to crops, which is why alfalfa grows less well in later years than earlier ones. Or maybe alfalfa depletes the soil of some other important nutrient or mineral, even though it doesn't deplete nitrogen.

Some kinds of ██████ ████ ████ ███████ ███ ███ ████ ██████████ ████ ████ ███ █████ █████ █████ █████ ██ ██████ ██████ ████ █████ █████ ████ █████ ██████ ██ █████ ███ █████

Incorrect. As far as we know, the stimulus is only talking about plants grown among their own kind: the same plants being grown in the same field. So knowing that "some plants" — and we don't know if alfalfa is one of these plants — grow better when grown among other plants than when on their own doesn't help us.

Alfalfa increases the ██████ ██ ████████ ██ ███ ████ ██ ██████ ████████ ████ ███ ███ ███ █████████ ██ ██ █ ████ ████ ██ ██████ ██ ████ █████ ██ ███████

Incorrect. (B) just explains how alfalfa increases the amount of nitrogen in the soil. It doesn't explain why alfalfa grows less well in later years than in earlier ones when planted in the same field, despite the fact that it increases nitrogen levels.

Certain types of ███████ █████████ ████████ ███████ ██████████ ████ ██████████ ██ ███ ████ ███ ████ ███ █████ ██ ███ ██████ ████ ███████ █████ ███████████

Correct. This explains why alfalfa grows less well in later years if planted in the same field in successive years. The problem isn't nitrogen depletion, since alfalfa fixes nitrogen. The problem is these substances that accumulate in the soil and are toxic to alfalfa.

84%

Alfalfa increases nitrogen ██ ███ ████ ██ █████ ██ █████ ████ ██ █ ███████ ████ ██ ████ ████████ ██ ███████ ██ ███ █████

Incorrect. If you picked (D), maybe you thought that the reason for alfalfa growth declining would be that, in some cases, this type of bacteria isn't present in a field, so the alfalfa's nitrogen-fixing quality doesn't work.

But the stimulus isn't talking about only some situations. It's talking about situations where alfalfa growth deteriorates over time even though the alfalfa is increasing the nitrogen in the soil — in other words, where this particular type of bacteria is present, according to (D). Remember from our pre-phrase that we're looking for some other cause than nitrogen depletion to explain what's going on with the alfalfa.

10%

Alfalfa is very █████████ ██ ████████ █ ████████ ████ ██ ██████ ████ ███ ██████ ██ █████ ██████ ██████

Incorrect. The stimulus never mentions black walnut trees, and (E) doesn't even specify how alfalfa reacts to this compound anyway.

Answer five questions and we'll estimate your score.

It takes about five minutes.

Take the free diagnostic

More free LSAT prep: Sample LSAT questions Full-length diagnostic & practice test All free LSAT resources

PrepTest 106 - Section 1 - Question 8

Answer five questions and we'll estimate your score.

Difficulty

Analysis

Answer Popularity

Question history

Confirm action

PrepTest 106 - Section 1 - Question 8

Answer five questions and we'll estimate your score.

Difficulty

Analysis

Answer Popularity

Question history

Want to know why the right answer is right?