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Respiration in Organisms — Science STD 7 — Question

Gujarat BoardEnglish MediumSTD 7ScienceRespiration in Organisms1 Mark
MCQ
The amount of oxygen in fresh air is:
  • A
    $18\%.$
  • ✓
    $21\%.$
  • C
    $23\%.$
  • D
    $24\%.$
✓

Answer

Correct option: B.
$21\%.$

At rest, an adult human inhales about $6 - 8$ litres of air per minute, of which two - third gets to the alveoli thus, takes part in gas exchange and the rest remaining in the air passages.
Fresh air contains $21\%$ oxygen and almost no carbon dioxide.

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