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WAEC Biology 2001 Question 21

Question 21

Respiration

The effect of the contraction of the muscles of the diaphram is that

  1. A.the volume of the thoracic cavity increases.
  2. B.more carbon dioxide is expelled through the nostrils.
  3. C.the rib cage is drawn inwards.
  4. D.the intercostal muscle becomes relaxed.
Show the answer and explanation

Answer: A (the volume of the thoracic cavity increases.)

Explanation

When the diaphragm contracts it flattens, making the chest cavity bigger, so air is drawn in.