PT105.S2.Q18

PrepTest 105 - Section 2 - Question 18

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In recent years the climate has been generally cool in northern Asia. ███ ██████ ███████ ████ ███ ███████ █████ ███████████ ███ ████████ ██ ████████ ████ ████ ████████ ██████ ████ █████ ██████ ██████ ███ ██████ ██ ████ █████ █████ █████ █████████ ██████████████ ██ ███ ████ ████████ ███ █████████ ███████ █████ ███████████ ███ ████████ ████████ ██████ █████ ███████ ███ ████████ ██ ██████ ███ █████ ███ ██████████ ███████ ████ ███ ██████ ██████ ██ ████ ██ ███ ████████ █████ ████ ████████ ██████ ███ ████ ████████

Summary: Surprising Phenomenon

The phenomenon we want to explain here is the scientists' prediction. If northern Asia, which has had a generally cool climate, has seen higher crop yields in periods when the average daily temperature and humidity have gone up, and the increased average daily temperature and humidity are supposed to become the norm over the next century, we might expect northern Asia to see higher crop yields over the next century as well. But the scientists predict that yearly yields of most crops from the area will go down, not up, over the next century.

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18.

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

a

Crop yields in ████████ ████ ███ ████████ ██ ██████ ████████ ████ █████ ███ ███████ █████ ███████████ ███ ████████ █████ ████████ ████ ██████ ███████
Incorrect. (A) tells us that in another region, crop yields are expected to stay the same even after the average daily temperature and humidity go up. We don't necessarily know if southern and northern Asia are comparable, and if they are, this just makes it more surprising that the scientists expect crop yields to decrease in northern Asia after a similar change in climate.
2%
b

Any increases in ███████████ ███ ████████ █████ ██ ███████████ ██ ██████ ██████ ██ ███████████ ██████ ████████ █████ ██ █████ ██ █████ ████████████
Incorrect. (B) tells us about an apparent benefit of increased temperature and humidity for plants. This doesn't explain why scientists expect crop yields to go down in conditions of increased temperature and humidity. If atmospheric carbon dioxide is "vital" — i.e., essential — to plant respiration, then increased temperature and humidity, by increasing atmospheric carbon dioxide levels, would presumably allow plants to thrive and crop yields to go up.
10%
c

The climate in ████████ ████ ███ █████████ ████ ███ ████ ███ ███ ██ ██████ █████ ███ ███████████ ██ ████ ████ ██████ █████ ██ ██████ ████████████
Correct. (C) helps explain the situation in the stimulus by bringing in a third factor: the presence (or absence) of these crop pests. So far, periods of increased temperature and humidity have seen significant increases in crop yields because the crops were able to benefit from the warmth and moisture without the downside of these insects, which couldn't thrive in the generally cool climate. After the increased warmth and humidity become the norm, these insect pests may become established and bring crop yields down as a result.
65%
d

In many parts ██ █████ ███ █████████ ██████ █████████████ ████ █████ ██████ ████ ██████ ███ ██████ ████████ █████ █████ ████ ██████ █████ ███████ ██ █████████
Incorrect. (D) just emphasizes why it's mysterious for the scientists to predict that, for northern Asia specifically, a warmer and wetter climate will cause crop yields to go down. In many other parts of Asia, such a change would cause most edible plants to thrive and so drive crop yields up.
3%
e

The recent climate ██ ████████ ████ ████████ ████ █████ ████ █████ ██████ █████ ██████ ███ ███████
Incorrect. (E) tells us that in northern Asia's recent climate — remember that the stimulus describes this recent climate as "generally cool" — the winters have been too cold for farming. But this doesn't explain why a warmer climate would cause crop yields to decrease. We don't know if the climate would become warm enough to allow farming during winter, but if it did, then we would expect crop yields to go up, not down, because people were farming for longer periods of the year. So (E) doesn't explain the phenomenon in the stimulus.
20%

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