Which one of the following is geseous growth regulator?

Options

A. IAA
B. NAA
C. IBA
D. Ethylene.

Answer

To determine which of the following is a gaseous growth regulator, we can analyze the options provided:

1. **IAA (Indole Acetic Acid)**: This is a type of auxin, which is a plant hormone that promotes growth. It is not gaseous.

2. **NAA (Naphthalene Acetic Acid)**: This is a synthetic auxin, similar to IAA, and is also not gaseous.

3. **IBA (Indole Butyric Acid)**: This is another type of auxin, specifically used for rooting. Like the previous two, it is not gaseous.

4. **Ethylene**: This is a gaseous plant hormone that acts as a growth regulator. Ethylene is known for its role in fruit ripening and can inhibit growth in certain contexts.

Based on this analysis, the gaseous growth regulator among the options is **Ethylene**.

### Step-by-Step Solution:
1. **Identify the Options**: Review the four options provided: IAA, NAA, IBA, and Ethylene.

2. **Analyze Each Option**:
- **IAA**: Recognize that it is a natural auxin and not gaseous.
- **NAA**: Identify it as a synthetic auxin, also not gaseous.
- **IBA**: Acknowledge it as another auxin, which is not gaseous.
- **Ethylene**: Confirm that it is a gaseous plant hormone.

3. **Determine the Correct Answer**: Conclude that Ethylene is the only gaseous growth regulator listed.

4. **Final Conclusion**: State that the correct answer to the question is Ethylene.