Passage Summary: Older bees go out for food and have bigger brains than the homebody younger bees. Because foraging is mentally taxing, scientists think the job itself grows the brain.

Conclusion: The activity of foraging is the cause of the increased brain size observed in older bees.

Reasoning: Older bees forage and have larger brains than younger bees who stay in the hive; since foraging is more cognitively demanding, it must be the reason for the size difference.

Analysis: This argument falls into the classic trap of confusing correlation with causation. Just because two things happen together—foraging and larger brains—doesn't mean one caused the other. To weaken this, look for an answer that suggests the brain growth happens naturally as the bee ages, regardless of its job, or perhaps that only bees who already have larger brains are 'promoted' to the foraging role.