Heads of Lettuce are

Options

A. Undeveloped inflorescence
B. Unopened flowers
C. Buds
D. Modified stems

Answer

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks about the nature of "heads of lettuce." We need to identify what they are classified as among the given options.

2. **Analyzing the Options**:
- **Undeveloped Inflorescence**: This refers to a cluster of flowers that have not yet developed. Lettuce heads do not fall into this category.
- **Unopened Flowers**: Similar to undeveloped inflorescence, unopened flowers are not the correct classification for lettuce heads.
- **Buds**: Buds are undeveloped shoots or flowers. While lettuce does have buds, the heads themselves are not classified as such.
- **Modified Stems**: This option suggests that the heads of lettuce are a form of stem that has been adapted for a specific function.

3. **Identifying the Correct Option**: The heads of lettuce are indeed modified stems. In some plants, the stem does not elongate during early development. Instead, it forms a short conical structure from which a crown of leaves arises. This is similar to how bulbs form in onions or heads in cabbage.

4. **Conclusion**: Therefore, the correct classification for the heads of lettuce is **modified stems**.

### Final Answer:
**Heads of lettuce are modified stems.**

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