Correct position of floral parts over thalamus in mustard plant is:

Options

A. Gynoecium occupies the highest position,while the other parts are situated below it.
B. Margin of the thalamus grows upward,enclosing the ovary completely, and other parts arise below the ovary
C. Gynoecium is present in the centre and other parts cover it partially.
D. Gynoecium is situated in the centre ,and other parts of the flower are located at the rim of the thalamus, at the same level

Answer

To determine the correct position of floral parts over the thalamus in the mustard plant, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Structure of the Flower**: In flowering plants, the arrangement of floral parts (sepals, petals, stamens, and gynoecium) on the thalamus (flower stalk) is crucial for identifying the type of flower.

2. **Identify the Type of Flower**: The mustard plant (Brassica) has a specific arrangement of its floral parts. It is classified as a hypogynous flower.

3. **Define Hypogynous Flower**: In a hypogynous flower, the ovary is situated above the other floral parts. This means that the gynoecium (female reproductive part) is at the highest position, and the other parts (stamens, petals, and sepals) are located below it.

4. **Analyze the Options**:
- **Option A**: Gynosium occupies the highest position while the other parts are situated below it. (This aligns with the definition of a hypogynous flower.)
- **Option B**: Margin of the thalamus grows upward enclosing the ovary completely and the other parts arise from below the ovary. (This describes a perigynous flower, not applicable here.)
- **Option C**: Gynosium is present in the center and other parts cover it partially. (This suggests a different arrangement, not applicable.)
- **Option D**: Gynosium is situated in the center and other parts of the flower are located at the rim of thalamus at the same level. (This describes an epigynous flower.)

5. **Conclusion**: Based on the analysis, the correct answer is **Option A**: Gynosium occupies the highest position while the other parts are situated below it.

### Final Answer:
**Option A**: Gynosium occupies the highest position while the other parts are situated below it.