A solid with an extended system of repeating covalent bonds is called a network solid.

Here's why:

* Covalent bonds are strong bonds that hold atoms together.

* Extended system means the bonds extend throughout the entire structure, creating a large, interconnected network.

* This creates a solid with a high melting point and strong, rigid structure.

Examples of network solids include:

* Diamond (carbon atoms connected in a tetrahedral network)

* Quartz (silicon and oxygen atoms connected in a tetrahedral network)

* Silicon carbide (silicon and carbon atoms connected in a tetrahedral network)