Assertion: B-cells (Beta cells) amount for about 80% of the total number of islet cells.
Reason: They secrete a hormone called thyroxine.

Options

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

Explanation

**Step-by-Step Solution:**

1. **Understanding the Assertion:**
- The assertion states that B-cells (Beta cells) account for about 80% of the total number of islet cells in the pancreas.
- The islets of Langerhans in the pancreas consist of different types of cells, including alpha cells, beta cells, and delta cells.

2. **Evaluating the Assertion:**
- Beta cells are indeed the most abundant cells in the islets of Langerhans, comprising approximately 60-80% of the total islet cell population.
- Therefore, the assertion that beta cells account for about 80% of the total number of islet cells is **true**.

3. **Understanding the Reason:**
- The reason states that beta cells secrete a hormone called thyroxine.
- Thyroxine is a hormone produced by the thyroid gland, not by the beta cells of the pancreas.

4. **Evaluating the Reason:**
- Beta cells actually secrete insulin, which is crucial for glucose metabolism.
- Since the reason incorrectly states that beta cells secrete thyroxine, the reason is **false**.

5. **Conclusion:**
- The assertion is true, but the reason is false.
- Therefore, the correct answer is that the assertion is true and the reason is false.

**Final Answer: Assertion True, Reason False.**

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