Assertion : Streptococcus thermophilus increases nitritional value of milk.
Reason : Curd and yoghurt have higher vitamin content than milk.

Options

A. If both assertion and reason are true and reason is the correct explanation of assertion
B. If both assertion and reason are true but reason is not the correct explanation of assertion
C. If assertion is true but reason is false
D. If both assertion and reason are false

Explanation

To solve the question regarding the assertion and reason provided, we can follow these steps:

### Step 1: Understand the Assertion
The assertion states that "Streptococcus thermophilus increases the nutritional value of milk."
- **Explanation**: Streptococcus thermophilus is a bacterium used in the fermentation process of milk to produce yogurt and curd. This bacterium plays a crucial role in converting lactose (milk sugar) into lactic acid, which not only helps in curd formation but also enhances the nutritional profile of the milk.

### Step 2: Understand the Reason
The reason states that "Curd and yogurt have higher vitamin content than milk."
- **Explanation**: During the fermentation process, the bacteria involved, including Streptococcus thermophilus and Lactobacillus bulgaricus, produce vitamins, particularly B vitamins, including B12. This results in curd and yogurt having a higher vitamin content compared to the original milk.

### Step 3: Evaluate the Truth of Both Statements
- Both the assertion and the reason are true.
- The assertion is true because Streptococcus thermophilus does enhance the nutritional value of milk.
- The reason is also true because curd and yogurt do indeed have a higher vitamin content than milk.

### Step 4: Determine the Relationship Between the Assertion and Reason
- The reason provides a correct explanation for the assertion. The increase in nutritional value (assertion) is due to the fermentation process that results in higher vitamin content (reason).

### Conclusion
Both the assertion and reason are true, and the reason correctly explains the assertion. Therefore, the correct answer is that both statements are true, and the reason is the correct explanation of the assertion.

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