Passage Summary: Some people think polar bears are great at finding their way home from unknown places because one bear did it once from a long distance.

Conclusion: Polar bears are capable of navigation, which is the ability to find one's way from unfamiliar territory to familiar points beyond sensory range.

Reasoning: A single polar bear successfully returned to its home territory after being released over 500 kilometers away.

Analysis: To weaken this, we need to show that the bear's return doesn't necessarily prove 'navigation' as defined. Perhaps the 500km area wasn't actually 'unfamiliar' to the bear, or maybe the bear didn't 'find its way' but rather stumbled upon it by accident. Look for an answer that suggests the bear had some other way of getting home or that the territory wasn't truly unfamiliar. This would undermine the specific evidence used to support the naturalists' claim.