The gas which forms carboxy-haemoglobin in blood, causing suffocation is

Options

A. carbon monoxide
B. nitrogen
C. carbon dioxide
D. chlorofluorocarbon

Explanation

To solve the question regarding the gas that forms carboxyhemoglobin in blood and causes suffocation, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Carboxyhemoglobin**:
- Carboxyhemoglobin is a compound formed when carbon monoxide binds to hemoglobin in the blood. It is important to differentiate it from other compounds like carbaminohemoglobin, which is formed with carbon dioxide.

2. **Identifying the Gas**:
- The question asks for the gas that forms carboxyhemoglobin. The term "carboxy" in carboxyhemoglobin refers specifically to carbon monoxide (CO), not carbon dioxide (CO2).

3. **Effects of Carboxyhemoglobin**:
- When carbon monoxide binds to hemoglobin, it prevents the hemoglobin from carrying oxygen effectively, leading to suffocation as the body is deprived of oxygen.

4. **Reviewing the Options**:
- The options provided are:
- A) Carbon monoxide
- B) Nitrogen
- C) Carbon dioxide
- D) Chlorofluorocarbon
- Among these, carbon monoxide is the correct answer as it specifically forms carboxyhemoglobin.

5. **Conclusion**:
- Therefore, the gas that forms carboxyhemoglobin in blood, causing suffocation, is carbon monoxide.

### Final Answer:
The gas which forms carboxyhemoglobin in blood, causing suffocation is **carbon monoxide**.