Each species of moth has an optimal body temperature for effective flight, and when air temperatures fall much below that...
GMAT Critical Reasoning : (CR) Questions
Each species of moth has an optimal body temperature for effective flight, and when air temperatures fall much below that temperature, the moths typically have to remain inactive on vegetation for extended periods, leaving them highly vulnerable to predators. In general, larger moths can fly faster than smaller ones and hence have a better chance of evading flying predators, but they also have higher optimal body temperatures, which explains why ______.
Which of the following most logically completes the passage?
Passage Analysis:
| Text from Passage | Analysis |
|---|---|
| Each species of moth has an optimal body temperature for effective flight, and when air temperatures fall much below that temperature, the moths typically have to remain inactive on vegetation for extended periods, leaving them highly vulnerable to predators. |
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| In general, larger moths can fly faster than smaller ones and hence have a better chance of evading flying predators |
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| but they also have higher optimal body temperatures |
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| which explains why _______ |
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Argument Flow:
The passage builds a logical chain: moths need optimal temperatures to fly → larger moths fly faster (advantage) → but larger moths need higher temperatures (disadvantage) → this temperature disadvantage must explain some outcome we need to identify
Main Conclusion:
The conclusion is incomplete, but it should explain a consequence of larger moths having higher optimal body temperatures that somehow balances out their flight speed advantage
Logical Structure:
This is a causal explanation structure where we're given competing factors (size advantages vs. temperature disadvantages) and need to identify what logical outcome results from this tradeoff between moth size and temperature requirements
Prethinking:
Question type:
Logically Completes - We need to find a statement that logically follows from the given facts about moth size, temperature requirements, and survival advantages/disadvantages
Precision of Claims
The claims involve comparative relationships: larger moths vs smaller moths in terms of flight speed, optimal body temperatures, and predator evasion abilities. The temperature requirements are presented as threshold conditions for flight capability
Strategy
Since this is a 'Logically Completes' question, we need to find what logical consequence naturally flows from the setup. We have two key facts in tension: (1) larger moths fly faster and escape predators better, but (2) larger moths need higher temperatures to fly. When we combine these with the opening fact that moths become vulnerable when temperatures drop below their optimal range, we should look for conclusions about how this temperature-size tradeoff affects moth survival or distribution patterns
This doesn't logically follow from the temperature information. The passage tells us larger moths fly faster, but says nothing about maneuverability. More importantly, this choice doesn't address the key issue about temperature requirements that the argument sets up. The conclusion should explain a consequence of the temperature disadvantage, not introduce a new flight advantage.
This logically flows from the temperature-size relationship. Since larger moths need higher optimal temperatures but become vulnerable when it's too cold, they would struggle more in cool climates where temperatures frequently drop below their high thresholds. In warm climates, they can more consistently maintain flight capability and use their speed advantage. This explains why the temperature disadvantage matters despite their flight speed advantage.
This introduces camouflage, which isn't mentioned anywhere in the passage. While this might help explain survival differences, it doesn't connect to the temperature requirements that the argument emphasizes. The conclusion should follow from the temperature-size relationship, not introduce entirely new survival factors.
This discusses wing proportions, which isn't supported by or connected to anything in the passage. The argument focuses on temperature requirements and flight speed, not wing structure. This choice doesn't explain any consequence of the temperature disadvantage that larger moths face.
This talks about predator behavior patterns but doesn't connect to the size-temperature relationship established in the passage. While predators are mentioned, this choice doesn't explain why the temperature requirements of large moths matter for the overall argument about moth survival.