In which process is the formation of carbon dioxide by yeast during fermentation clearly seen?

Correct answer: Rising of dough

The governing concept is alcoholic fermentation by yeast. In the absence of sufficient oxygen, yeast breaks down glucose and forms ethanol and carbon dioxide. When yeast is mixed with dough, the released carbon dioxide becomes trapped as bubbles in the dough’s gluten network. These bubbles expand during resting or heating, making the dough rise. Therefore A is correct; blood clotting, urine formation, and stomatal closure do not use yeast fermentation.