Which of the following is not properly matched?

Options

A. Formaldehyde -carcinogenic
B. Sulphur dioxide- respiratory problems
C. Nitrogen oxide-brown air
D. Mean annual temperature-`25^(@)C`

Answer

To determine which of the following options is not properly matched, we will analyze each option one by one.

### Step 1: Analyze the first option
- **Formaldehyde causes immunogenic**:
- Formaldehyde is known to be a carcinogenic agent, classified by the EPA (Environmental Protection Agency) as a cancer-causing substance. It has been linked to leukemia incidences.
- **Conclusion**: This option is correctly matched.

### Step 2: Analyze the second option
- **Sulfur dioxide causes respiratory problems**:
- Sulfur dioxide is indeed known to cause respiratory issues, including asthma and bronchitis. It is a significant air pollutant that affects the respiratory tract.
- **Conclusion**: This option is also correctly matched.

### Step 3: Analyze the third option
- **Nitrogen oxide causes brown hair**:
- Nitrogen oxides are known to contribute to air pollution and can cause respiratory problems. However, they are referred to as "brown air" due to the light absorption properties of nitrogen dioxide, which can give a brownish appearance to polluted air.
- **Conclusion**: This option is correctly matched.

### Step 4: Analyze the fourth option
- **Mean annual temperature causes 25 degrees centigrade**:
- The mean annual temperature is an average that can vary significantly based on geographical location, climate, and weather conditions. It is not fixed at 25 degrees centigrade; rather, it can be higher or lower depending on the area.
- **Conclusion**: This option is incorrectly matched.

### Final Conclusion
The option that is not properly matched is:
- **Mean annual temperature causes 25 degrees centigrade**.