The mucus produced by the goblet cells
(a) moistens the incoming air
(b) trap the fine dust particles
(c) filter out large dust particles
(d) warms the incoming air .

Options

A. (I) a, b , c are correct
B. (2) only a is correct
C. (3) b and d are correct
D. (4) a and c are incorrect

Answer

To answer the question regarding the function of mucus produced by goblet cells, we can analyze each option step by step.

### Step-by-Step Solution:

1. **Understanding Mucus**:
- Mucus is a viscous fluid produced by goblet cells, which are found in various tissues, including the respiratory tract. Its primary role is to protect and lubricate surfaces.

2. **Analyzing Option (a)**:
- **Moistens the incoming air**:
- Mucus helps to humidify the air that we breathe in. As air passes through the nasal passages, it comes into contact with mucus, which adds moisture to the air.
- **Conclusion**: This statement is correct.

3. **Analyzing Option (b)**:
- **Traps the fine dust particles**:
- The sticky nature of mucus allows it to capture and hold onto fine dust particles and other small debris present in the air.
- **Conclusion**: This statement is also correct.

4. **Analyzing Option (c)**:
- **Filters out large dust particles**:
- Mucus can trap larger dust particles as well, preventing them from entering the respiratory system.
- **Conclusion**: This statement is correct too.

5. **Analyzing Option (d)**:
- **Warms the incoming air**:
- While mucus does not directly warm the air, the nasal passages themselves can help to warm the air as it passes through. However, mucus primarily serves to moisten and trap particles rather than warm the air.
- **Conclusion**: This statement is incorrect.

6. **Final Conclusion**:
- Based on the analysis, options (a), (b), and (c) are correct regarding the functions of mucus produced by goblet cells, while option (d) is incorrect.

### Final Answer:
The mucus produced by the goblet cells:
- (a) moistens the incoming air
- (b) traps the fine dust particles
- (c) filters out large dust particles

Thus, the correct answer is options A, B, and C are correct.