Passage Summary: Even though Pluto is large and has an atmosphere, it isn't a real planet because it originally started out orbiting Neptune before being kicked out.

Conclusion: Pluto is not a true planet.

Reasoning: Pluto formed in orbit around Neptune and was later ejected from that orbit due to the gravitational capture of Triton.

Analysis: The author provides a specific historical fact about Pluto's origin and uses it to disqualify Pluto from 'true planet' status. However, the premises never actually define what a 'true planet' is. To make this argument logically airtight, we need a rule that explicitly links Pluto's history to its status. Look for an answer that states something like: 'Any body that formed in orbit around a planet cannot be considered a true planet.' This would guarantee the conclusion based on the evidence provided.