The Respiratory System

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Across
  1. 3. we breathe in through ... or mouth
  2. 4. the oxygen in the air then moves from the lungs into the ...
  3. 5. the air we breathe in contains ... gas
  4. 6. something that protects our respiratory system
Down
  1. 1. the air moves down the ... and into our lungs
  2. 2. we breathe out air that contains ... gas