Which of the following set is not natural plant growth regulator

Options

A. `GA_(3)`, IAA, 2IP
B. IAA, 2IP, Zn
C. ABA, IBA, `GA_(3)`
D. ABA, `GA_(3)`, IAA

Answer

To solve the question, "Which of the following set is not a natural plant growth regulator?" we need to analyze the options provided and identify which substances are classified as natural plant growth regulators.

### Step-by-Step Solution:

1. **Identify the Options**:
The options provided are:
- A: GA3, IAA, 2IP
- B: IAA, 2IP, Zinc
- C: ABA, IBA, GA3
- D: ABA, GA3, IAA

2. **Understand Plant Growth Regulators**:
Plant growth regulators (or hormones) are classified into five main groups:
- Auxins (e.g., Indole-3-acetic acid - IAA)
- Gibberellins (e.g., GA3)
- Cytokinins (e.g., 2IP)
- Abscisic Acid (ABA)
- Ethylene

3. **Analyze Each Option**:
- **Option A**: GA3 (Gibberellin), IAA (Auxin), 2IP (Cytokinin) - All are natural plant growth regulators.
- **Option B**: IAA (Auxin), 2IP (Cytokinin), Zinc - IAA and 2IP are natural regulators, but Zinc is a micronutrient, not a plant growth regulator.
- **Option C**: ABA (Abscisic Acid), IBA (Indole-3-butyric acid, an Auxin), GA3 (Gibberellin) - All are natural plant growth regulators.
- **Option D**: ABA (Abscisic Acid), GA3 (Gibberellin), IAA (Auxin) - All are natural plant growth regulators.

4. **Conclusion**:
The only option that includes a substance that is not a natural plant growth regulator is **Option B**: IAA, 2IP, Zinc.

### Final Answer:
**Option B: IAA, 2IP, Zinc** is the set that is not entirely composed of natural plant growth regulators.