Step 1: Identify the yeast used in bread-making.
S. cerevisiae, commonly known as baker's yeast, is used in bread-making as it ferments sugars to produce carbon dioxide, causing the bread to rise.
Step 2: Analyze the options.
Aspergillus is a genus of molds, not used for bread-making.
Streptobacillus is a genus of bacteria, not used in baking.
S.octosporus is not a yeast species used in bread-making.
Conclusion: The correct answer is (A) S. cerevisiae.