The answer is B. Bacteria.

Bread is made by fermenting dough with yeast, which is a type of fungus. Curd is made by fermenting milk with bacteria.

A. Fungi is incorrect because fungi are not used to make curd. C. Germs is incorrect because germs is a general term that can refer to any type of microorganism, including bacteria, viruses, and fungi. D. Virus is incorrect because viruses are not used to make curd.