Multiple choice general knowledge

Which animal sleeps with one eye open?

  1. Sharks

  2. Eels

  3. Dolphins

  4. Hydra
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Dolphins sleep with one eye open due to unihemispheric slow-wave sleep - they shut down one half of their brain at a time while the other half remains alert. This allows them to continue breathing consciously (they're voluntary breathers) and watch for predators even while resting.

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