The correct option is C Curd Lactobacillus belongs to the group of bacteria which perform fermentation and convert the sugars into lactic acid in the absence of oxygen. This bacterium is present in the raw milk. This bacterium can also be added to the milk in the form of already synthesized curd where they multiplies and lactose sugar into lactic acid. The lactic acid which is produced gives a sour taste and the milk is converted to curd. These organisms are present in very high number in curd.