“Impure air is purified in the presence of light and green plants” was first said by

Options

A. De Saussure
B. Priestley
C. Van Helmont
D. Ingenhousz

Explanation

**Step-by-Step Solution:**

1. **Identify the Statement**: The question states, "Impure air is purified in the presence of light and green plants."

2. **Historical Context**: This statement relates to the early studies of photosynthesis and the role of plants in air purification.

3. **Key Figure**: The person who first made this statement is Joseph Priestley, an English chemist and clergyman.

4. **Priestley's Experiment**: Joseph Priestley conducted a famous experiment known as the "Bell Jar Experiment." In this experiment, he used a bell jar to observe the effects of plants on air quality.

5. **Details of the Experiment**:
- He placed a mouse, a candle, and a green plant inside a sealed bell jar.
- When the candle was lit, it consumed oxygen and produced carbon dioxide, which eventually led to the death of the mouse due to lack of oxygen.
- However, when the plant was present, it absorbed the carbon dioxide and released oxygen through the process of photosynthesis, allowing the mouse to survive.

6. **Conclusion**: Therefore, the statement about impure air being purified in the presence of light and green plants can be attributed to Joseph Priestley.

**Final Answer**: Joseph Priestley.

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