Which one of the following affects chlorophyll?

Options

A. Sulphur dioxide
B. Nitrogen oxides
C. Carbon monoxide
D. Both 1 and 2

Answer

To solve the question "Which one of the following affects chlorophyll?" we need to analyze the options provided and understand the impact of each on chlorophyll.

### Step-by-step Solution:

1. **Understanding Chlorophyll**:
- Chlorophyll is a green pigment found in plants that is crucial for photosynthesis. It absorbs light energy, primarily from the blue and red parts of the light spectrum, and converts it into chemical energy.

2. **Identifying the Options**:
- The options given are:
1. Sulphur Dioxide (SO₂)
2. Nitrogen Oxide (NO)
3. Carbon Monoxide (CO)
4. Both 1st and 2nd (Sulphur Dioxide and Nitrogen Oxide)

3. **Researching the Effects of Each Gas**:
- **Sulphur Dioxide (SO₂)**: This gas is known to be harmful to plants. It can lead to chlorosis (yellowing of leaves) and can damage chlorophyll, affecting photosynthesis.
- **Nitrogen Oxide (NO)**: Similar to sulphur dioxide, nitrogen oxides can also have detrimental effects on plant health, including the degradation of chlorophyll.
- **Carbon Monoxide (CO)**: While carbon monoxide is a pollutant, it does not directly affect chlorophyll or the photosynthesis process in the same way that sulphur dioxide and nitrogen oxides do.

4. **Analyzing the Options**:
- From the research, we find that both sulphur dioxide and nitrogen oxides are harmful to chlorophyll. Therefore, the correct answer must include both of these gases.
- Option 4 states "Both 1st and 2nd," which correctly identifies that both sulphur dioxide and nitrogen oxides affect chlorophyll.

5. **Conclusion**:
- The correct answer to the question is **Option 4: Both 1st and 2nd**.

### Final Answer:
**Option 4: Both 1st and 2nd (Sulphur Dioxide and Nitrogen Oxide)**.