Which one is not matched?

Options

A. Turmeric : Metallic yellow
B. Fryon : Chloro-fluorocarbon
C. Greenhouse gas : `CO_2`
D. Contour agriculture : Soil erosion

Explanation

To determine which option is not matched correctly, we will analyze each option provided in the question.

### Step-by-Step Solution:

1. **Analyze Option A: Turmeric - Metallic Yellow**
- Turmeric contains a compound called curcumin, which is responsible for its characteristic yellow color. Thus, this option is correctly matched.
- **Hint:** Look for the key compounds in natural substances that give them their colors.

2. **Analyze Option B: Fryon - Chlorofluorocarbon**
- The term "Fryon" is incorrect; the correct term is "Freon." Freon is indeed a type of chlorofluorocarbon (CFC). Therefore, this option is not matched correctly due to the spelling error.
- **Hint:** Pay attention to the correct spelling of chemical compounds and their classifications.

3. **Analyze Option C: Greenhouse Gas - CO2**
- Carbon dioxide (CO2) is a well-known greenhouse gas and is primarily responsible for the greenhouse effect. This option is correctly matched.
- **Hint:** Remember that greenhouse gases include CO2, methane, and others that trap heat in the atmosphere.

4. **Analyze Option D: Contour Agriculture - Soil Erosion**
- Contour agriculture is a farming practice used on sloped land to reduce soil erosion. It involves plowing and planting across the slope of the land, which helps to conserve soil and water. This option is also correctly matched.
- **Hint:** Consider agricultural practices and their environmental impacts, especially in relation to soil conservation.

### Conclusion:
After analyzing all options, it is clear that **Option B: Fryon - Chlorofluorocarbon** is the one that is not matched correctly because of the incorrect spelling of "Freon."

### Final Answer:
**Option B is not matched correctly.**