PrepTest 109, Section 2, Question 15
Experts anticipate that global atmospheric concentrations of carbon(445 more words not shown)
Which one of the following(8 more words not shown)
- AElevated levels of(12 more words not shown)
- BRecent studies have(14 more words not shown)
- CThe possible beneficial(15 more words not shown)
- DIncreased levels of(18 more words not shown)
- EIncreased levels of(14 more words not shown)
Reading the passage
We've already predicted that the supposed silver lining isn't something we can count on. Extra CO2 may help plants grow, but weeds can benefit more than crops, and decomposing peat can release more CO2 than the extra vegetation absorbs.
What we’re looking for
We want that criticism of the promised benefits. Simply saying that plant growth increases, or that global warming is bad, won't capture it.
Working the answers
- A
More plant growth is accepted, but greater agricultural yields aren't guaranteed. Weeds may crowd out the crops we want. A repeats the optimistic forecast that the rest of the discussion challenges.
- B
The studies don't have to contradict one another. Plants can grow more while crop yields fall, because weeds gain more than crops. Extra vegetation can also absorb CO2 while decomposition releases even more. The problem is what people concluded from increased growth.
- CCorrect
This covers both overstatements: abundant crops and slower warming. The research shows why increased growth doesn't guarantee either benefit. That's the specific objection we predicted.
- D
A smaller boost isn't the same as inhibited growth. Corn can benefit yet lose ground to weeds that benefit more. D also leaves out the separate issue of decomposition and warming.
- E
This gives us extra growth and a bad climate outcome, so it's tempting. But the argument challenges the predicted slowdown; it doesn't make this definite forecast about the ultimate global warming rate. E also omits the agricultural issue. C captures the criticism without turning it into a broader prediction.
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