In the 1930s C.B. van Niel correctly hypothesized that oxygen atoms in the oxygen gas released by plants come from

Options

A. `H_(2)O`
B. `CO_(2)`
C. `C_(6)H_(12)O_(6)`
D. `O_(3)`

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks about the source of oxygen atoms released by plants during photosynthesis, as hypothesized by C.B. van Niel in the 1930s.

2. **Background Knowledge**: C.B. van Niel conducted experiments using photosynthetic bacteria, specifically purple sulfur bacteria and green sulfur bacteria, to study the process of photosynthesis.

3. **Key Experiment**: In his experiments, van Niel demonstrated that photosynthesis involves light-dependent reactions where hydrogen is derived from an oxidizable compound. He used hydrogen sulfide (H2S) in his studies, which led to the release of sulfur instead of oxygen.

4. **Formulation of Hypothesis**: Van Niel hypothesized that the oxygen produced during photosynthesis does not come from carbon dioxide (CO2) but rather from water (H2O). This was a significant conclusion that shifted the understanding of the source of oxygen in photosynthesis.

5. **Chemical Equation**: The general equation for photosynthesis can be represented as:
\[ 6CO_2 + 6H_2O \rightarrow C_6H_{12}O_6 + 6O_2 \]
In this equation, it is clear that the oxygen (O2) released is a product of the splitting of water molecules.

6. **Conclusion**: Based on van Niel's hypothesis and the chemical equation for photosynthesis, the oxygen atoms released by plants during photosynthesis come from water.

7. **Final Answer**: Therefore, the correct answer to the question is **water**.

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