In the experiment to determine the speed of sound using a resonance column,

Options

A. (a)prongs of the tuning fork are kept in a vertical plane
B. (b)prongs of the tuning fork are kept in a horizontal plane
C. (c)in one of the two resonances observed, the length of the resonating air column is close to the wavelength of sound in air
D. (d)in one of the two resonances observed, the length of the resonating air column is closed to half of the wavelength of sound in air

Explanation

To determine the speed of sound using a resonance column, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Setup**:
- We need to visualize the experimental setup for determining the speed of sound. The setup typically includes a cylindrical vessel filled with air and a tuning fork that produces sound waves.

2. **Draw the Diagram**:
- Sketch a cylindrical vessel (resonance column) and indicate the position of the tuning fork above it. The tuning fork's prongs should be shown in a vertical orientation, as this is crucial for the experiment.

3. **Identify the Components**:
- The cylindrical vessel represents the medium (air) through which sound travels. The tuning fork generates sound waves that will resonate within the column.

4. **Understand Resonance**:
- When the frequency of the tuning fork matches the natural frequency of the air column, resonance occurs. This results in standing waves being formed in the column.

5. **Determine the Correct Statement**:
- The key aspect of the experiment is that the prongs of the tuning fork must be kept in the vertical plane to ensure that the sound waves propagate effectively into the air column.

6. **Check the Options**:
- Review the provided options to identify which statement correctly reflects the setup. In this case, the correct statement is that "the prongs of the tuning fork are kept in the vertical plane."

### Conclusion:
The correct answer is that the prongs of the tuning fork are kept in the vertical plane.