Choose the correct statement.

Options

A. (a) Solution culture (hydroponics ) contains all essential elements except one, the usefulness of which is to be determined
B. (b) In Aeroponics roots are dipped in solution culture rich in air
C. (c) Potometer is used to measure degree of opening of stomata
D. (d) All of the above

Answer

To solve the question "Choose the correct statement," we will analyze each statement provided and determine which one is true.

### Step 1: Analyze Statement A
- **Statement A**: "Solution culture or hydroponics contain all essential elements except one the usefulness of which is to be determined."
- **Analysis**: This statement is true. Hydroponics is a method of growing plants without soil, using a mineral nutrient solution that provides all essential nutrients for plant growth. The statement correctly describes the nature of hydroponics.

### Step 2: Analyze Statement B
- **Statement B**: "In aeroponics, the roots are dipped in solution culture rich in air."
- **Analysis**: This statement is false. In aeroponics, the roots of the plants are suspended in the air and are misted with a nutrient solution. They are not dipped in a solution; instead, they receive nutrients through misting.

### Step 3: Analyze Statement C
- **Statement C**: "Photometer is used to measure the degree of opening stomata."
- **Analysis**: This statement is also false. A potometer is used to measure the rate of water loss from leaves, while the degree of opening of stomata is measured using a porometer. Therefore, this statement is incorrect.

### Step 4: Analyze Statement D
- **Statement D**: "All of the above."
- **Analysis**: Since statements B and C are false, statement D cannot be true.

### Conclusion
After analyzing all the statements, we find that only Statement A is correct. Therefore, the correct answer is:

**Correct Answer: A**

---