Which of the following don't occur naturally ?

Options

A. IAA
B. IBA
C. NAA
D. Both (A) and (B)

Answer

To solve the question "Which of the following don't occur naturally?" we need to analyze the options provided and identify which compounds are natural and which are synthetic.

### Step-by-Step Solution:

1. **Identify the Compounds**: The options given are:
- IAA (Indole-3-acetic acid)
- IBA (Indole butyric acid)
- NAA (Naphthalene acetic acid)
- Both A and B

2. **Understand Natural vs. Synthetic Auxins**:
- **IAA (Indole-3-acetic acid)**: This is a well-known natural auxin that is produced by plants. Therefore, it occurs naturally.
- **IBA (Indole butyric acid)**: This is also a natural auxin that has been isolated from plants. Thus, it occurs naturally as well.
- **NAA (Naphthalene acetic acid)**: This is a synthetic auxin, meaning it is not found naturally in plants but is instead created artificially for agricultural purposes.

3. **Evaluate the Options**:
- Since IAA and IBA both occur naturally, they cannot be the correct answer.
- NAA, being synthetic, does not occur naturally.
- The option "Both A and B" is incorrect since both A (IAA) and B (IBA) are natural.

4. **Conclusion**: The only compound that does not occur naturally is NAA (Naphthalene acetic acid).

### Final Answer:
NAA (Naphthalene acetic acid) does not occur naturally.

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