Exoskeleton of cockroach is ……………… .

Explanation

**Step-by-Step Solution:**

1. **Understanding Exoskeleton**: The exoskeleton is an external skeleton that provides support and protection to the body of an organism. In the case of cockroaches, it serves as a protective layer.

2. **Composition of Exoskeleton**: The exoskeleton of a cockroach is primarily made up of a protein called chitin. Chitin is a long-chain polymer that is a key component in the structure of the exoskeleton.

3. **Sclerotization**: The exoskeleton of cockroaches is described as sclerotized. Sclerotization refers to the process where the chitin is hardened, making the exoskeleton tough and durable. This hardening is crucial for the protection of the cockroach.

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