Passage Summary: It is easy to form a planet where life could live, but hard to form the big 'bodyguard' planets like Jupiter that protect them. Since these bodyguards are rare, smart life probably won't happen often.

Conclusion: The probability of intelligent life developing on a planet is low because large planets, which are necessary for protection, are rare.

Reasoning: While life-supporting planets are common, the large planets required to shield them from comets are rare, and without that shield, intelligent life cannot arise.

Analysis: The argument assumes that the rarity of large planets directly translates to a low probability for intelligent life across the board. To evaluate this, we need to know if every intelligent-life-bearing planet requires a large planet for protection, or if there are other ways to survive comet strikes. Look for an answer that asks about the necessity or frequency of this specific protective mechanism in other planetary systems.