Reason of lung cancer is

Options

A. coal mining
B. calcium fluoride
C. cement factory
D. bauxite mining

Explanation

### Step-by-Step Solution:

1. **Identify Major Causes**: The primary cause of lung cancer is smoking. This includes both active smoking (directly smoking tobacco) and passive smoking (inhaling smoke from others).

2. **Consider Occupational Hazards**: Another significant cause of lung cancer is exposure to certain occupational hazards, such as working in a cement factory.

3. **Understand Chemical Exposure**: In cement factories, workers are often exposed to dry cement dust, which contains various harmful chemicals.

4. **Impact on Mucous Membranes**: These chemicals can irritate the mucous membranes in the lungs, nostrils, and other areas of the body. The mucous membranes play a crucial role in protecting the respiratory system and maintaining moisture.

5. **Chronic Irritation and Inflammation**: Prolonged exposure to these irritants leads to chronic irritation of the mucous membranes. Over time, this irritation can result in inflammation.

6. **Link to Cancer Development**: Chronic inflammation is a known risk factor for cancer development. Continuous irritation and inflammation of lung tissues can eventually lead to the development of lung cancer.

### Summary:
The main reasons for lung cancer include:
- **Smoking**: Both active and passive smoking are significant risk factors.
- **Occupational Exposure**: Long-term exposure to harmful substances, such as those found in cement dust, can lead to lung cancer through mechanisms of irritation and inflammation of the lung tissues.