Who demonstrated for the first time that in photosynthesis, oxygen is evolved from water

Options

A. Ruben and kamen
B. Calvin
C. R. Hill
D. Govindji.

Answer

**Step-by-Step Solution:**

1. **Identify the Question**: The question asks who first demonstrated that oxygen is evolved from water during photosynthesis.

2. **Historical Context**: Understanding the history of photosynthesis research is important. Before Robert Hill's work, the exact source of oxygen produced during photosynthesis was not clearly established.

3. **Key Scientist**: The scientist who first demonstrated that oxygen comes from water during photosynthesis is Robert Hill.

4. **Experimental Setup**: In 1939, Robert Hill conducted experiments using chloroplasts extracted from the leaves of plants, specifically the species Stellaria media.

5. **Procedure**: He suspended the chloroplasts in a test tube containing an electron acceptor and potassium pyrophosphate.

6. **Observation**: Hill observed that oxygen was released due to the photochemical splitting of water. This process is known as photolysis.

7. **Important Note**: During Hill's experiment, no carbon dioxide was consumed, and no carbohydrates were formed, indicating that the oxygen evolved was solely from the water.

8. **Conclusion**: Thus, the correct answer to the question is Robert Hill, as he was the first to demonstrate that oxygen is evolved from water during photosynthesis.

**Final Answer**: Robert Hill

---