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

Options

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

Answer

To solve the question of how many mineral elements are obtained from the soil or crust of the earth among the given options (Magnesium, Sulphur, Oxygen, Phosphorus, Carbon, and Potassium), we will analyze each element one by one.

### Step-by-Step Solution:

1. **Identify the Elements**: The elements we need to evaluate are:
- Magnesium
- Sulphur
- Oxygen
- Phosphorus
- Carbon
- Potassium

2. **Evaluate Each Element**:
- **Magnesium**: This element is obtained from the soil in the form of magnesium ions (Mg²⁺).
- **Sulphur**: Sulphur is also found in the soil, typically in the form of sulfate ions (SO₄²⁻).
- **Oxygen**: Oxygen is primarily obtained from the atmosphere and is not sourced from the soil.
- **Phosphorus**: Phosphorus is available in the soil as phosphate ions (H₂PO₄⁻ and HPO₄²⁻).
- **Carbon**: Carbon is mainly obtained from the atmosphere, particularly through the process of photosynthesis.
- **Potassium**: Potassium is found in the soil in the form of potassium ions (K⁺).

3. **Count the Elements from Soil**:
- From the analysis:
- Magnesium: Yes (from soil)
- Sulphur: Yes (from soil)
- Oxygen: No (from atmosphere)
- Phosphorus: Yes (from soil)
- Carbon: No (from atmosphere)
- Potassium: Yes (from soil)

4. **Total Count**: The elements obtained from the soil are Magnesium, Sulphur, Phosphorus, and Potassium. That gives us a total of **4 elements**.

### Final Answer:
The total number of mineral elements obtained from the soil or crust of the earth is **4**.