Multiple choice general knowledge

Who sleep with one eye open?

  1. Owl

  2. Whales

  3. Dolphins

  4. Bat
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Certain whale species, including dolphins (which are toothed whales), sleep with one eye open. This is called unihemispheric slow-wave sleep - one half of the brain sleeps while the other half stays awake to control breathing and watch for predators. Owls, bats, and other mammals do sleep with both eyes closed, though they may be active at night.

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