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 introducing the natural phenomenon of intermittent mass loss with regard to Asteroid 6478 Gault and notes that it curiously has not lost mass at its perihelion like other asteroids typically do. The text then refutes "solar energy–driven ice vaporization" and "the singular nature of impact ejection" as two possible explanations for Asteroid 6478 Gault’s intermittent mass loss. Finally, the text presents Luu et al.’s explanation that "6478 Gault is shedding mass due to rotational instability," which the author says is "likely correct." Thus, the overall structure of the text is that it introduces a natural phenomenon, refutes two potential explanations for that phenomenon, and then presents a third explanation for that phenomenon that the author regards as plausible.
Why the other choices are wrong
Choice A
Choice A is incorrect because the text doesn’t distinguish between multiple observations. It focuses on the single observation that Asteroid 6478 Gault is losing mass and evaluates multiple explanations for the phenomenon. The text also asserts that Luu et al.’s explanation is credible and "likely correct."
Choice B
Choice B is incorrect because the text describes a natural phenomenon, not a specific astronomical finding. In addition, although the text does note flawed reasons for Asteroid 6478 Gault’s intermittent mass loss, it doesn’t mention that Asteroid 6478 Gault’s intermittent mass loss is based on new evidence.
Choice D
Choice D is incorrect. Although the text does evaluate explanations for the cause of Asteroid 6478 Gault’s intermittent mass loss, the text also asserts that Luu et al.’s explanation that they have put forth is persuasive and "likely correct."