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WAEC Biology 2026 Question 21

Question 21

Respiration

In a practical class, baker's yeast was added to a bread dough that rose after 30 minutes. The gas responsible for the rise observed in the dough is

  1. A.carbon(IV) oxide
  2. B.oxygen
  3. C.nitrogen (IV) oxide
  4. D.carbon(II) oxide
Show the answer and explanation

Answer: A (carbon(IV) oxide)

Explanation

Yeast ferments the sugar in dough and releases carbon (IV) oxide, whose bubbles make the dough rise.