માનવમાં, શ્વાસ છોડવામાં આવેલા હવામાં ઓક્સિજન લગભગ ________ હોય છે.

Inhaled air has about 21% oxygen. The body absorbs only part of it, so exhaled air still contains about 16% oxygen, along with about 4% carbon dioxide; this is why mouth-to-mouth resuscitation works.