Homing pigeons are famous for their ability to find their way home from great distances, a skill often attributed to visual landmarks. However, researchers have found that pigeons can navigate even when landmarks are obscured by fog. This led scientists to discover that pigeons possess magnetoreception—the ability to detect the Earth's magnetic field. Special cells in the pigeon's beak act as a biological compass, allowing them to determine direction regardless of visibility.
Which choice best describes the overall structure of the text?
It notes a common belief about navigation, presents a contradictory observation, and explains the biological mechanism that accounts for it.
It explains the anatomy of a pigeon, compares it to other birds, and concludes that pigeons are superior navigators.
It describes a failed experiment involving fog, then proposes a new theory that has yet to be tested.
It lists the various ways humans use compasses, then compares human navigation to bird migration.
Correct Answer: A
Choice A is the best answer. The text starts with a common belief (visual landmarks). It presents a contradictory finding (fog doesn't stop them). It explains the mechanism (magnetoreception).
Choice B is incorrect. It doesn't compare them to other birds or call them "superior." Choice C is incorrect. The experiment (fog) worked; it wasn't a failure. Choice D is incorrect. No comparison to human compass use.