Passage Summary: Scientists found unique meteorites that could only have come from Mercury, Venus, or Mars; since Mercury is too close to the Sun and Venus has too much gravity for rocks to escape, the author concludes the rocks must have come from Mars.

Conclusion: The meteorites found in Shergotty likely originated on Mars.

Reasoning: The meteorites must have come from a geologically active planet (Mercury, Venus, or Mars), but Mercury and Venus are ruled out due to solar capture and gravitational pull, respectively.

Analysis: This argument employs a classic 'process of elimination' strategy to reach its conclusion. It begins by establishing a limited set of possibilities—the three geologically active planets—and then provides evidence to disqualify all but one of those candidates. In 'Method of Reasoning' questions with this structure, look for an answer choice that describes the systematic ruling out of alternative explanations to support the sole remaining option. The author identifies a specific pool of candidates and uses the physical characteristics of those candidates to narrow the field down to a single probable source.