Analogy — Bread : Yeast :: Curd : ? Select the microorganism typically responsible for curd formation, analogous to yeast in bread making.

Introduction / Context:
In food technology, bread rises due to yeast (a fungus) fermenting sugars and producing carbon dioxide. For curd (yogurt), the typical agents are lactic acid bacteria (e.g., Lactobacillus spp.) that ferment lactose to lactic acid, coagulating milk proteins. The analogy matches “product : characteristic microbe.”

Given Data / Assumptions:

• Bread : yeast (microbial agent).
• Curd : lactic acid bacteria (microbial agent).
• We need the specific category that makes curd, not a vague or incorrect class.

Concept / Approach:
Preserve the “food item : principal microorganism” relation. While yeast are fungi, curd is not typically produced by fungi or viruses. “Germs” is imprecise. The correct, standard class is “bacteria.”

Step-by-Step Solution:

Verification / Alternative check:
Dairy science references consistently attribute curd/yogurt fermentation to bacterial cultures (e.g., Lactobacillus bulgaricus, Streptococcus thermophilus).

Why Other Options Are Wrong:

• Fungi — describes yeast but not the typical agents for curd.
• Germs — non-technical catch-all; lacks specificity.
• Virus — not used in curd formation.

Common Pitfalls:
Generalizing from bread (fungus) and assuming the same kingdom for curd; food fermentations vary in agent type.

Final Answer:
Bacteria