In bread-making, bakeries use yeast because it makes the bread soft and spongy. Yeast is a microorganism that ferments the dough, causing it to rise. When yeast is added to the dough, it consumes the sugars present, releasing carbon dioxide gas as a byproduct. This gas gets trapped in the dough, causing it to expand and give the bread its airy texture. As a result, the bread becomes soft and spongy. Other options are not correct. Option 1, suggesting that yeast makes the bread hard, is incorrect because yeast actually helps to make the bread rise and become fluffy. Option 3, stating that yeast enhances food values, is not entirely accurate because yeast primarily affects the texture of the bread rather than its nutritional content. Option 4, claiming that yeast keeps the bread fresh, is not directly related to yeast, but rather factors such as preservatives and packaging.