Yeast Fermentation Causes Dough to Rise

Steps:

• Equal dough mixtures in X and Y are left to ferment in warmth.
• Y shows expansion due to gas production from yeast activity.
• Carbon dioxide gas from fermentation forms bubbles in Y's dough.
• X lacks this gas, remaining unchanged.

Why B is correct:

• In bread dough, yeast ferments sugars to produce CO₂ gas (C₆H₁₂O₆ → 2C₂H₅OH + 2CO₂), trapping bubbles that leaven and expand the dough.

Why the others are wrong:

• A. Alcohol is a byproduct of fermentation but remains liquid and does not cause rising.
• C. Lactic acid results from bacterial fermentation in yogurt or sourdough, not standard yeast bread rising.
• D. Oxygen is consumed by yeast during initial growth, not produced to cause expansion.

Final answer: B