PrepTest 102, Section 2, Question 15
Some plants have extremely sensitive biological thermometers.(62 more words not shown)
Which one of the following,(8 more words not shown)
- ANeither rhododendrons nor(37 more words not shown)
- BMany people find(16 more words not shown)
- CThe climate and(16 more words not shown)
- DAir temperature surrounding(38 more words not shown)
- ECertain types of(27 more words not shown)
Reading the argument
The plants seem to bracket the temperature neatly.
Below 0°C, the rhododendron leaves curl. We see uncurled leaves, which puts the temperature at 0°C or above. Above 2°C, mature crocus blossoms open. We see unopened blossoms, which puts the temperature at 2°C or below. Put those limits together and the claimed range is 0°C to 2°C. A thermometer reading 1°C would then be within one degree.
I can see why that reasoning initially looks persuasive. What could make it fail?
Maybe the plants take time to respond. If the temperature has just changed, the leaves or blossoms might not yet show the expected effect. Or perhaps illness, damage, or some other influence could interfere with the response. Those are possibilities to investigate, not botanical facts we can add to the passage.
What we’re looking for
For the weakener, I'd look for a reason these observations don't reliably establish the thermometer's accuracy.
Working the answers
- A
We aren't observing rhododendron blossoms. We're observing rhododendron leaves, alongside mature crocus blossoms. The two species having different flowering seasons doesn't prevent that combination. A would be more relevant if the proposed test required both kinds of blossom at once, but it doesn't. The observed leaves can supply their information regardless of when the rhododendrons flower.
- B
Whether people enjoy standing outdoors in the cold doesn't determine whether the temperature reading is accurate. An uncomfortable observer could still perform an accurate check. The question concerns the evidence supplied by the plants, not the observer's comfort.
- C
Compatible growing conditions could help explain why we find the plants together. That doesn't make the proposed temperature check less reliable. It gives no reason to doubt the inference drawn from the specified leaves and blossoms.
- DCorrect
The plants may be experiencing different temperatures. The rhododendron's leaves can be far above the crocus blossoms, and D says the surrounding air temperatures can differ by more than 2°C even when the plants grow side by side.
Now we can't combine the two limits into one narrow range. Imagine the leaves are in air at 5°C while the crocus blossoms are in air at −1°C. Uncurled leaves and unopened blossoms both fit the rules. Yet a thermometer near the leaves reading 1°C would be four degrees off. The initial reasoning treats two local temperature readings as if they constrain the same temperature. D gives a reason that may be false.
- E
Some thermometers being less accurate in certain ranges doesn't show that this thermometer is in such a range, or explain why the plant-based check fails. We aren't given its type or the boundaries of those ranges. A general possibility of inaccuracy doesn't directly undermine the specific evidence offered to verify this reading.
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