PrepTest 148, Section 4, Question 15
Global warming has contributed to a rise in(66 more words not shown)
Which one of the following(12 more words not shown)
- AThe exact magnitude(10 more words not shown)
- BRises in global(14 more words not shown)
- CLittle is known(13 more words not shown)
- DThe amount of(23 more words not shown)
- EThe amount of(24 more words not shown)
Reading the argument
The sea level isn't responding to just one thing. Melting ice adds water, and warming also expands water that is already there. Then the reservoirs push the other way by holding back water that would otherwise reach the sea.
What we’re looking for
My first thought is that more water must be accumulating somewhere on land. But be careful about how far to take that. The passage gives us artificial reservoirs holding a large amount of water; it doesn't establish that natural lakes and rivers have all risen. It also doesn't tell us that the water in those reservoirs came specifically from melting glaciers. For the inference, we should stay with those stated processes and what they let us conclude.
Working the answers
- A
Explaining several influences on sea level doesn't tell us that people disagree about the size of the rise. Its magnitude might be disputed or might be agreed upon. The passage doesn't discuss a disagreement about measurement.
- B
Before the reservoirs existed, melting ice and the expansion of warming water could still have helped explain rising seas. The passage doesn't describe those earlier rises as mysterious. The reservoirs affect how much water reaches the sea; their absence doesn't erase the other explanations.
- C
The passage identifies ways global warming contributes: melting ice and expansion of heated water. It doesn't assess how much scientists know overall about those contributions. We can't turn this explanation of several processes into the broad claim that little is known.
- D
We have no quantities establishing this equality. The reservoirs contain a great deal of water, but that doesn't mean their total matches the water produced by melting glaciers and ice sheets. The passage also doesn't say all reservoir water is meltwater. D adds a numerical comparison that hasn't been supplied.
- ECorrect
Sea-level rise alone doesn't isolate the amount of melting ice. Some of the rise comes from water expanding, which can increase volume without the addition of meltwater. At the same time, reservoirs withhold water that would otherwise contribute to sea level. Without accounting for those other effects, we can't read the amount of glacier and ice-sheet melt directly from the total rise.
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