Comprehension: Read the given passage and answer the questions that follow.…
2025
Comprehension:
Read the given passage and answer the questions that follow.
One potential cause of human extinction is global warming, but even without human-induced climate change, the sun's increasing radiation will eventually bring about our demise. A 2014 article in Science presents two models for this countdown, one more pessimistic than the other. Researchers from Pennsylvania State University, led by Ravi Kopparapu, predicted that with a 6% increase in solar radiation, in 150 million years, only underwater life and some resilient microbes will remain. According to this model, our species could be extinct within this timeframe.
Alternatively, if Earth's temperatures rise more gradually, we might have 600 to 700 million years left, based on the "Kopparapu model."
Wolf and Toon argue that we have 1.5 billion years left. Eventually, habitable territory would shrink to a strip around the poles. The ultimate end will come much later, in about four billion years, when the sun goes out. As the sun becomes a "red giant," it could strip away Earth's atmosphere, leaving a magma-covered surface with metal oxide icebergs floating on it.
These projections underscore the finite nature of our existence on this planet, emphasizing the importance of understanding and preparing for these eventualities.
According to Wolf and Toon, when will the ultimate end come?
- A.
600 to 700 million years
- B.
1.5 billion years
- C.
4 billion years
- D.
3 billion years
Attempted by 1 students.
Show answer & explanation
Correct answer: C
Concept
In a "according to X" reading-comprehension question, the correct answer is the fact the passage explicitly attributes to the named source X — the number, date, or claim stated in the sentence introduced by or immediately following that source's name, with no competing attribution from another named source in between.
Application
The passage lays out two separate estimates, each tied to a named source. The Kopparapu-led team (Pennsylvania State University) is credited with the 150-million-year pessimistic figure and, under a more gradual-warming scenario, the alternative 600-to-700-million-year figure — both explicitly tied to "the Kopparapu model." The passage then introduces a second, independent estimate: "Wolf and Toon argue that we have 1.5 billion years left." Everything that follows this sentence, up to the next new topic (the sun becoming a red giant and stripping Earth's atmosphere), continues within the Wolf-and-Toon estimate, since no other named researcher appears in between: "Eventually, habitable territory would shrink to a strip around the poles. The ultimate end will come much later, in about four billion years, when the sun goes out." The question asks specifically for the timeframe "the ultimate end" comes according to Wolf and Toon, and the passage states this directly: about four billion years.
Cross-check
600 to 700 million years is the Kopparapu model's gradual-warming alternative to its own 150-million-year pessimistic estimate — attributed to the Kopparapu team, not to Wolf and Toon.
1.5 billion years is the number of years Wolf and Toon estimate remain before habitable territory shrinks to a strip around the poles — an intermediate stage in their timeline, not "the ultimate end."
3 billion years is not stated anywhere in the passage.
The ultimate end, according to Wolf and Toon, comes in about four billion years, when the sun goes out — so "4 billion years" is correct.