Suberin in cork wall is a

Options

A. polypeptide
B. polysaccharide
C. fatty substance
D. none of the above.

Explanation

### Step-by-Step Solution:

1. **Understanding Suberin**:
- Suberin is a substance found in the cork walls of plants. It is known for its properties and functions.

2. **Characteristics of Suberin**:
- Suberin is described as an "inert waxy substance." This means it does not react easily with other substances and has a waxy texture.

3. **Function of Suberin**:
- One of the major functions of suberin is its impermeability. It acts as a barrier, preventing water and solutes from passing through. This is crucial for protecting the plant.

4. **Chemical Composition**:
- Suberin is composed of long chains of fatty acids and glycerols. This composition contributes to its waxy nature and impermeable properties.

5. **Analyzing the Options**:
- **Polypeptide**: Incorrect. Polypeptides are made of amino acids, which is not the case for suberin.
- **Polysaccharide**: Incorrect. Polysaccharides are long chains of monosaccharides (sugars), which does not describe suberin.
- **Fatty substances**: Correct. Suberin is indeed a fatty substance due to its composition of fatty acids and glycerol.
- **None of the above**: Incorrect, as we have identified that suberin is a fatty substance.

6. **Conclusion**:
- Based on the analysis, the correct answer is that suberin in cork walls is a **fatty substance**.