Passage Summary: The amygdala helps us feel fear, and people who lose it usually don't feel afraid. However, if those same people breathe in too much carbon dioxide, they feel intense fear anyway.

Reasoning: The amygdala is the brain's primary fear center, and its destruction usually prevents fear, yet high carbon dioxide levels still trigger extreme fear in people without an amygdala.

Analysis: This set of facts points toward a biological 'workaround' for fear. If the part of the brain responsible for fear is gone, but a specific stimulus like carbon dioxide still causes fear, then the amygdala cannot be the only way the brain processes that emotion. We are looking for an inference that acknowledges fear can be triggered through multiple pathways. Don't look for a grand discovery; look for a modest statement that fits the evidence provided.