Multiple choice

Which of the following animals sleeps without closing its eyes?

  1. Whales

  2. Buffalo

  3. Ostrich

  4. Dolphin
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Dolphins have the remarkable ability to sleep with one eye open. This is possible because they sleep with one half of their brain at a time (unihemispheric sleep), allowing them to maintain some consciousness and continue breathing voluntarily. None of the other animals listed have this particular sleeping adaptation.

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