Plant growth regulators (PGRs) are

Options

A. Simple organic substance of different chemical composition
B. Complex organic substances of different chemical composition
C. Simple and complex organic substances of same chemical composition
D. Small organic substances of same chemical composition

Answer

### Step-by-Step Solution

1. **Understanding Plant Growth Regulators (PGRs)**:
- Plant growth regulators, also known as phytohormones, are substances that influence plant growth and development. They play crucial roles in various physiological processes.

2. **Identifying the Nature of PGRs**:
- PGRs can be classified based on their chemical composition. They include various types of hormones such as auxins, gibberellins, cytokinins, ethylene, and abscisic acid (ABA).

3. **Analyzing the Options**:
- The question provides four options regarding the composition of PGRs:
- A) Simple organic substances of different chemical composition
- B) Complex organic substances of different chemical composition
- C) Simple and complex organic substances of the same chemical composition
- D) Small organic substances of the same chemical composition

4. **Evaluating the Correct Option**:
- PGRs are primarily simple organic substances (like auxins and gibberellins) that have different chemical compositions. This aligns with option A.

5. **Conclusion**:
- Therefore, the correct answer is **A) Simple organic substances of different chemical composition**.