The correct answer is option 'C' - Ruben, Hassid, and Kamens. These scientists conducted an experiment in the 1940s that provided evidence for the fact that oxygen evolved in photosynthesis comes from water.

Here is a detailed explanation of their experiment:

1. Background:
Prior to Ruben, Hassid, and Kamens' experiment, it was known that plants produce oxygen during photosynthesis. However, the origin of this oxygen was not clearly understood.

2. Experimental setup:
Ruben, Hassid, and Kamens used the alga Chlorella, which is capable of performing photosynthesis, for their experiment. They grew the alga in the presence of water that contained a heavy isotope of oxygen called O-18. This isotope can be traced and distinguished from the normal oxygen isotope, O-16.

3. Isotopic labeling:
The researchers labeled the oxygen in the water with O-18 by bubbling the algal culture with O-18 labeled water. This allowed them to track the movement of the labeled oxygen during photosynthesis.

4. Radioactive tracer:
To further track the oxygen, Ruben, Hassid, and Kamens introduced a radioactive tracer, carbon-14, into the carbon dioxide surrounding the algal culture. This allowed them to monitor the movement of carbon during photosynthesis.

5. Radioactive oxygen production:
After exposing the algal culture to light, the researchers observed that radioactive oxygen (O-18) was produced. This indicated that the oxygen evolved during photosynthesis originated from the water labeled with O-18.

6. Carbon fixation:
Additionally, the researchers found that the radioactive carbon (carbon-14) from the carbon dioxide was fixed into organic compounds by the alga. This confirmed that carbon dioxide is the source of carbon during photosynthesis.

7. Conclusion:
Based on their findings, Ruben, Hassid, and Kamens concluded that the oxygen evolved in photosynthesis comes from water. This experiment provided direct evidence for the source of oxygen in photosynthesis and helped clarify the overall process of photosynthesis.

In summary, Ruben, Hassid, and Kamens used isotopic labeling and a radioactive tracer to demonstrate that the oxygen evolved in photosynthesis is derived from water. This experiment significantly contributed to our understanding of the process of photosynthesis and the role of water in oxygen production.