Answers

2016-03-30T21:54:32+05:30
Oxygen is the life giver as it is necessary for us to live on Earth. In the past, there would be possibilities that the concentration of oxygen probably fluctuated at time so there would be little direct effect on life. Therefore by this humans evolved and lived.
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2016-03-30T22:03:12+05:30
Idiot They can't survive they will die
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