Which one of the following is not a synthetic auxin?
(a) 2, 4-D
(b) 2, 4, 5-T
(c) NAA
(d) IAA

Options

A. 2, 4-D
B. 2, 4, 5-T
C. NAA
D. IAA

Answer

To determine which of the following is not a synthetic auxin, we need to analyze each option provided:

1. **Understanding Auxins**: Auxins are plant hormones that promote growth. They can be classified into natural and synthetic auxins.

2. **Identifying the Options**:
- **(a) 2, 4-D**: This is a synthetic auxin commonly used as a herbicide.
- **(b) 2, 4, 5-T**: This is also a synthetic auxin and is used similarly as a herbicide.
- **(c) NAA**: Naphthalene acetic acid (NAA) is another synthetic auxin used in agriculture.
- **(d) IAA**: Indole acetic acid (IAA) is the most common natural auxin found in plants.

3. **Conclusion**: Since IAA (option d) is a natural auxin, it is the correct answer to the question, as it is not a synthetic auxin.

**Final Answer**: (d) IAA

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