How many of the following mineral elements are obtained from soil or crust of the earth?
Magnesium
sulphur
oxygen
phosphorus
carbon
potassium

Options

A. 4
B. 5
C. 6
D. 3

Answer

To determine how many of the listed mineral elements are obtained from the soil or crust of the Earth, we will analyze each element one by one.

1. **Magnesium**:
- Magnesium is absorbed by plants from the soil in the form of magnesium ions (Mg²⁺).
- Therefore, magnesium is obtained from the soil.

2. **Sulfur**:
- Sulfur is also absorbed from the soil, primarily in the form of sulfate ions (SO₄²⁻).
- Thus, sulfur is obtained from the soil.

3. **Oxygen**:
- Oxygen is not absorbed from the soil; instead, it is taken directly from the atmosphere through the process of photosynthesis.
- Therefore, oxygen is not obtained from the soil.

4. **Phosphorus**:
- Phosphorus is absorbed from the soil in the form of orthophosphate ions (H₂PO₄⁻ or HPO₄²⁻).
- Hence, phosphorus is obtained from the soil.

5. **Carbon**:
- Carbon is not obtained from the soil; it is absorbed from the atmosphere during photosynthesis.
- Therefore, carbon is not obtained from the soil.

6. **Potassium**:
- Potassium is absorbed from the soil in the form of potassium ions (K⁺).
- Thus, potassium is obtained from the soil.

Now, let's summarize the findings:
- Elements obtained from soil: Magnesium, Sulfur, Phosphorus, Potassium (4 elements).
- Elements not obtained from soil: Oxygen, Carbon (2 elements).

**Final Answer**: 4 elements are obtained from the soil or crust of the Earth.