Curd is formed due to the presence of bacterium:

Options

A. Lactobacillus
B. Streptococcus
C. Bacillus
D. None of these

Explanation

**Step-by-Step Solution:**

1. **Identify the Bacteria Responsible for Curd Formation:**
Curd is primarily formed due to the action of specific bacteria present in milk. The most notable bacterium responsible for this process is Lactobacillus.

2. **Understanding the Role of Lactobacillus:**
Lactobacillus is a type of gram-positive, rod-shaped bacterium. It plays a crucial role in the fermentation process of milk.

3. **Fermentation Process:**
During the fermentation process, Lactobacillus bacteria convert lactose (the sugar found in milk) into lactic acid. This conversion is essential for the thickening of milk and the formation of curd.

4. **Conclusion:**
Based on the information provided, the correct answer to the question is that curd is formed due to the presence of the bacterium Lactobacillus.

**Final Answer:**
Curd is formed due to the presence of the bacterium Lactobacillus.

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