A natural growth regulator is

Options

A. NAA
B. Ethylene
C. 2, 4-D
D. Benzaldehyde

Answer

To determine which of the given options is a natural growth regulator, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Definition of Growth Regulators**:
- Growth regulators are substances that regulate the growth of plants. They can be classified based on their origin into natural and synthetic growth regulators.

2. **Identify Natural Growth Regulators**:
- Natural growth regulators are produced by plants themselves. They are also referred to as endogenous hormones. Examples include auxins, gibberellins, cytokinins, ethylene, and abscisic acid.

3. **Differentiate Between Natural and Synthetic Growth Regulators**:
- Synthetic growth regulators are artificially produced and mimic the physiological activities of natural hormones. Examples include 2,4-D, NAA, and IBA.

4. **Analyze the Given Options**:
- The options provided are:
- A) NAA (synthetic)
- B) Ethylene (natural)
- C) 2,4-D (synthetic)
- D) Benzaldehyde (synthetic)

5. **Select the Correct Option**:
- From the analysis, ethylene is the only option that is classified as a natural growth regulator.

### Conclusion:
The correct answer is **B) Ethylene**, as it is a natural growth regulator produced by plants.

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