The correct answer is C. Lacto-bacillus.
Lacto-bacillus is a genus of Gram-positive, facultative anaerobic, rod-shaped bacteria. They are a major part of the lactic acid bacteria (LAB), which are a group of bacteria that produce lactic acid as a metabolic end product. LAB are widely distributed in nature, and they are found in many different environments, including soil, water, and the human body.
LAB are important in many industrial processes, including the production of cheese, yogurt, and sauerkraut. They are also used in the production of probiotics, which are live bacteria that are beneficial to human health.
Lacto-bacillus are also important in the fermentation of milk to produce curd. The process of curdling milk involves the addition of LAB to milk, which convert the lactose in milk into lactic acid. The lactic acid lowers the pH of the milk, which causes the casein proteins in milk to coagulate and form curds.
The other options are incorrect. Lycopodium is a genus of clubmosses. Yeast is a single-celled fungus. Fungus is a large and diverse group of organisms that includes mushrooms, molds, and yeasts.