Which component of cigarette smoke reduces `O_2` concentration in the body

Options

A. Nicotine
B. Carcinogens
C. Cilicotoxins
D. Carbonmonoxide

Answer

### Step-by-Step Solution:

1. **Understanding Cigarette Smoke Composition**: Cigarette smoke contains various harmful components, including tar, nicotine, and gases such as carbon monoxide (CO).

2. **Identifying the Harmful Component**: Among these components, carbon monoxide is a significant gas that is produced when tobacco is burned.

3. **Mechanism of Action**: When a person smokes a cigarette, carbon monoxide enters the bloodstream. It has a much higher affinity for hemoglobin (the molecule in red blood cells that carries oxygen) than oxygen itself.

4. **Impact on Oxygen Transport**: Because carbon monoxide binds to hemoglobin more effectively than oxygen, it reduces the amount of oxygen that can be transported in the blood. This leads to a deficiency of oxygen in the body tissues.

5. **Conclusion**: Therefore, the component of cigarette smoke that reduces O2 concentration in the body is carbon monoxide.

### Final Answer:
The component of cigarette smoke that reduces O2 concentration in the body is carbon monoxide.