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The Brainliest Answer!
2015-06-28T15:24:03+05:30
We yawn when our brain needs more oxygen as when we yawn we open a big mouth and take air(oxygen) in.. so basically yawning is done when we are tired..
thanks.. :)
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2015-06-28T16:06:14+05:30
Because the oxygen the our body is less
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