Assertion :- ADH is secreted by hypothalamus.
Reason:- Changes in osmotic pressure are noted by osmoreceptors present in the hypothalamus.

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.

Answer

### Step-by-Step Solution:

1. **Understanding the Assertion**: The assertion states that "ADH is secreted by the hypothalamus." This is true because Antidiuretic Hormone (ADH), also known as vasopressin, is synthesized in the hypothalamus and then transported to the posterior pituitary gland for secretion into the bloodstream.

2. **Understanding the Reason**: The reason states that "Changes in osmotic pressure are noted by osmoreceptors present in the hypothalamus." This is also true. Osmoreceptors in the hypothalamus detect changes in the osmotic pressure of the blood, which helps regulate the release of ADH.

3. **Analyzing the Relationship**: While both the assertion and the reason are true, the reason does not directly explain why ADH is secreted by the hypothalamus. The secretion of ADH is a response to the detection of changes in osmotic pressure, but the assertion specifically refers to the site of secretion rather than the mechanism of regulation.

4. **Evaluating the Options**:
- Option 1 states that both the assertion and reason are true, and the reason is the correct explanation of the assertion. This is incorrect because the reason does not explain the assertion directly.
- Option 2 states that both assertion and reason are true, but the reason is not the correct explanation of the assertion. This is correct.
- Option 3 states that the assertion is true and the reason is false. This is incorrect because both statements are true.
- Option 4 states that both assertion and reason are false. This is incorrect as well.

5. **Conclusion**: The correct answer is Option 2: Both assertion and reason are true, but the reason is not the correct explanation of the assertion.