The correct answer is A. Fungus.
Yeast is a single-celled fungus that is used in baking to make bread rise. It is a living organism that converts sugar into carbon dioxide and alcohol. The carbon dioxide bubbles cause the dough to rise, and the alcohol evaporates during baking.
Bacteria are also single-celled organisms, but they are not fungi. Bacteria are much smaller than yeast cells, and they do not have a nucleus. Bacteria can cause diseases, but they can also be used to make yogurt, cheese, and other fermented foods.
Seeds are the reproductive units of plants. They contain an embryo plant and a food supply that the embryo uses to grow. Seeds are usually enclosed in a protective coat.
Plants are multicellular organisms that are photosynthetic. They make their own food using sunlight, water, and carbon dioxide. Plants have roots, stems, leaves, and flowers.
In conclusion, yeast is a fungus that is used in baking to make bread rise. It is a living organism that converts sugar into carbon dioxide and alcohol. The carbon dioxide bubbles cause the dough to rise, and the alcohol evaporates during baking.