Which of the following is not a natural auxin

Options

A. Indole acetic acid
B. Naphthalene acetic acid
C. Indole acetaldehyde
D. Indole ethanol.

Answer

To determine which of the following is not a natural auxin, we can analyze the given options:

1. **Indole Acetic Acid (IAA)**: This is the most common naturally occurring auxin found in plants. It plays a significant role in plant growth and development.

2. **Naphthalene Acetic Acid (NAA)**: This is a synthetic auxin, which means it is not naturally occurring in plants. It is often used as a rooting agent in horticulture.

3. **Indole Acetate**: This is a form of indole acetic acid and is considered a natural auxin.

4. **Indole Ethanol**: This is also a naturally occurring auxin found in plants.

From this analysis, we can conclude that **Naphthalene Acetic Acid (NAA)** is not a natural auxin.

### Step-by-Step Solution:
1. **Identify the Auxins**: List the options provided and identify which ones are known to be natural auxins.
2. **Research Each Option**:
- Indole Acetic Acid (IAA) - natural auxin.
- Naphthalene Acetic Acid (NAA) - synthetic auxin.
- Indole Acetate - natural auxin.
- Indole Ethanol - natural auxin.
3. **Conclusion**: Determine which option is not a natural auxin based on the research.

### Final Answer:
Naphthalene Acetic Acid (NAA) is not a natural auxin.