What role does yeast play in baking?

Yeast plays a crucial role in the baking process, primarily by providing leavening and promoting rise in dough. When yeast is activated, it ferments sugars present in the flour and other ingredients, producing carbon dioxide gas and alcohol as byproducts. The carbon dioxide gas is what creates bubbles in the dough, causing it to expand and rise. This fermentation process not only contributes to the texture of the baked product but also helps develop complex flavors, contributing to the overall quality of bread and other yeast-leavened baked goods.

While yeast does have some influence on flavor due to the fermentation process, its most significant function is clearly its role in leavening. Other substances like baking powder or baking soda can also act as leavening agents, but yeast is unique because it continues to develop flavor as it ferments during rising and baking. This makes option B the definitive choice when considering the primary role of yeast in baking.