Which of the following is not an inorganic nutrient for plants?

Options

A. Water
B. Carbon dioxide gas
C. Mineral ions
D. Nitrogen gas

Answer

To determine which of the following is not an inorganic nutrient for plants, we need to analyze each option provided:

1. **Water**: This is an essential inorganic nutrient for plants. It is crucial for photosynthesis and serves as a solvent for nutrients.

2. **Carbon Dioxide (CO2)**: This is also an inorganic nutrient. Plants utilize carbon dioxide during photosynthesis to produce glucose.

3. **Mineral Ions**: These are inorganic nutrients that include various essential minerals (like potassium, calcium, magnesium, etc.) that plants absorb from the soil.

4. **Nitrogen Gas (N2)**: While nitrogen is essential for plant growth, it is not taken up by plants in its gaseous form (N2). Plants absorb nitrogen primarily in the form of ammonia (NH3) or nitrate (NO3-).

Based on this analysis, the correct answer to the question "Which of the following is not an inorganic nutrient for plants?" is:

**Nitrogen Gas (N2)**.

### Step-by-Step Solution:
1. **Identify the options**: Water, Carbon Dioxide, Mineral Ions, Nitrogen Gas.
2. **Analyze each option**:
- Water: Inorganic nutrient.
- Carbon Dioxide: Inorganic nutrient.
- Mineral Ions: Inorganic nutrients.
- Nitrogen Gas: Not an inorganic nutrient as it is not directly absorbed by plants.
3. **Conclusion**: Nitrogen is absorbed in forms other than gas, making Nitrogen Gas the correct answer.