Mark the correctly matched pair :

Options

A. `NO_(x)` - Carcinogen
B. CO - Asphyxia
C. PAN - Primary pollutant
D. PAN - Classical smog

Answer

To solve the question "Mark the correctly matched pair," we will analyze each option provided and determine which one is correct.

### Step-by-Step Solution:

1. **Analyze the first pair: Nitrous Oxide and Carcinogen**
- Nitrous oxide (N2O) is known as a greenhouse gas and is not classified as a carcinogen. Carcinogens are substances that can lead to cancer. Therefore, this pair is **incorrect**.

2. **Analyze the second pair: Carbon Monoxide and Asphyxia**
- Carbon monoxide (CO) is a colorless, odorless gas that has a high affinity for hemoglobin in the blood. When inhaled, it binds to hemoglobin more effectively than oxygen, leading to a deficiency of oxygen in the body, which causes asphyxia. Thus, this pair is **correct**.

3. **Analyze the third pair: PAN and Primary Pollutant**
- PAN (Peroxyacetyl Nitrate) is not a primary pollutant; it is classified as a secondary pollutant. Secondary pollutants are formed in the atmosphere through chemical reactions. Therefore, this pair is **incorrect**.

4. **Analyze the fourth pair: PAN and Classical Smoke**
- PAN is not classical smoke; it is a physiochemical smoke formed from the reaction of nitric oxide and hydrocarbons. Therefore, this pair is also **incorrect**.

### Conclusion:
The only correctly matched pair is **Carbon Monoxide and Asphyxia**.

### Final Answer:
The correct answer is **Option B: Carbon Monoxide and Asphyxia**.

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