Example of a network covalent solid is:

Options

A. `SO_(2)` (solid)
B. `H_(2)O` (ice)
C. `I_(2)`
D. Diamond

Explanation

To determine an example of a network covalent solid, we need to understand the characteristics of network covalent solids and how they differ from other types of solids.

### Step-by-Step Solution:

1. **Understanding Network Covalent Solids**:
- Network covalent solids are characterized by a continuous network of covalent bonds throughout the material. This means that each atom is bonded to several other atoms, forming a three-dimensional structure.

2. **Identifying the Options**:
- We need to look at the given options and identify which one represents a network covalent solid. Common examples include diamond, silicon carbide (SiC), and quartz (SiO2).

3. **Analyzing Other Types of Solids**:
- Compare the options with known types of solids:
- **Molecular Solids**: These are held together by intermolecular forces such as hydrogen bonds, dipole-dipole interactions, or van der Waals forces. Examples include H2O (water) and SO2 (sulfur dioxide).
- **Ionic Solids**: These consist of ions held together by ionic bonds, such as NaCl (table salt).
- **Metallic Solids**: These consist of metal atoms bonded by metallic bonds, allowing for conductivity.

4. **Identifying the Correct Answer**:
- Among the options, diamond is a classic example of a network covalent solid. In diamond, each carbon atom is tetrahedrally bonded to four other carbon atoms, creating a robust three-dimensional network.

5. **Conclusion**:
- Therefore, the correct answer is diamond, as it exemplifies the characteristics of a network covalent solid.

### Final Answer:
The example of a network covalent solid is **diamond**.