Explanation
Correct answer: C.
Choice C is the best answer because it most accurately describes the overall structure of the text. The text begins by discussing the detection of phosphine gas in Venus’s atmosphere, indicating that it is unexpected because on Earth, phosphine derives from biological sources, and Venus is thought to be uninhabitable, thereby lacking in biological sources. The text then presents the effort by Bains et al. to determine whether one or more abiotic (nonbiological) pathways could explain the observed levels of phosphine on Venus, noting that none could. Finally, the text notes an implication: if phosphine exists on Venus, its presence would indicate that our current understanding of chemical processes on Venus that could produce it is inadequate. Thus, the text introduces an unexpected observation about Venus’s atmosphere, presents an effort to investigate mechanisms related to that observation, and notes an implication of that effort’s findings.
Why the other choices are wrong
Choice A
Choice A is incorrect. The text starts by mentioning that phosphine has been detected in Venus’s atmosphere. Rather than discuss whether the presence of phosphine on Venus can be confirmed, the text focuses on the efforts of one team of researchers, Bains et al., who are trying to explain the observed amount of phosphine on Venus. Furthermore, the text doesn’t suggest that the research team was skeptical about the presence of phosphine on Venus.
Choice B
Choice B is incorrect because, rather than indicating a consensus view about the phosphine detected on Venus, the text focuses on the fact that the detection “remains controversial,” a framing that suggests the controversy is not a new phenomenon. The text also doesn’t suggest that future atmospheric observations would be needed to settle the controversy. There is no consensus view about the presence of phosphine on Venus.
Choice D
Choice D is incorrect because the text does not compare levels of phosphine on Venus with levels on Earth, nor does it address practical challenges of studying the gas on Venus.