Assertion : Mucous membrane immobilises the micro-organisms in the body.
Reason : Microoganisms and dust particles entering the respiratory tract are trapped in the mucus.

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 assertin 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 "Mucous membrane immobilizes the microorganisms in the body." This is true because mucous membranes act as a barrier to pathogens and help in trapping them.

2. **Understanding the Reason**: The reason provided is that "Microorganisms and dust particles entering the respiratory tract are trapped in the mucus." This is also true as mucus serves to trap these particles, preventing them from entering deeper into the respiratory system.

3. **Connecting Assertion and Reason**: Since both the assertion and the reason are true, we need to determine if the reason correctly explains the assertion. The reason explains how the mucous membrane immobilizes microorganisms by trapping them in mucus.

4. **Conclusion**: Both the assertion and the reason are true, and the reason is indeed the correct explanation of the assertion. Therefore, the correct answer is that both the assertion and reason are true, and the reason is the correct explanation of the assertion.

**Final Answer**: Option 1: Both assertion and reason are true, and reason is the correct explanation of assertion.

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