The technique of growing plants in nutrient solution complete absence of soil, can be employed as for
A. Identification of essentiality of mineral elements
B. Commercial production of vegetables
C. Identification of deficiency symptoms of mineras
D. Conservation of rare plant species:

Options

A. Only A is correct
B. Only D is incorrect
C. Only A and C are correct
D. Only A and Care incorrect

Answer

To answer the question regarding the technique of growing plants in nutrient solution in the complete absence of soil, we will analyze each option provided:

1. **Understanding Hydroponics**: The technique being referred to is hydroponics, where plants are grown in a nutrient-rich solution instead of soil. This method allows for precise control over the nutrients that plants receive.

2. **Option A: Identification of essentiality of mineral elements**: Hydroponics can be used to identify which mineral elements are essential for plant growth. By varying the nutrient solutions and observing plant growth, researchers can determine the necessity of specific minerals. This option is correct.

3. **Option B: Commercial production of vegetables**: Hydroponics is widely used for the commercial production of various vegetables such as tomatoes, cucumbers, and lettuce. This method allows for efficient growth and high yield in a controlled environment. This option is also correct.

4. **Option C: Identification of deficiency symptoms of minerals**: By manipulating the nutrient solutions, researchers can induce specific mineral deficiencies in plants and observe the resulting symptoms. This helps in identifying which minerals are lacking and their effects on plant health. This option is correct as well.

5. **Option D: Conservation of rare plant species**: While hydroponics can be beneficial for growing plants, it is not primarily used for the conservation of rare plant species. This option is incorrect.

**Conclusion**: The correct answers are A, B, and C. The technique of growing plants in nutrient solution in complete absence of soil can be employed for the identification of essentiality of mineral elements, commercial production of vegetables, and identification of deficiency symptoms of minerals.