_________ are generally non-malleable and nonductile.

Explanation

**Step-by-Step Solution:**

1. **Understanding Malleability and Ductility**:
- Malleability refers to the ability of a substance to be hammered or pressed into thin sheets without breaking.
- Ductility refers to the ability of a substance to be stretched into thin wires.

2. **Identifying the Characteristics of Metals**:
- Metals are typically known for their malleability and ductility. For example, metals like aluminum can be easily shaped into thin sheets (malleable) or drawn into wires (ductile).

3. **Identifying Non-Malleable and Non-Ductile Substances**:
- The question specifically asks for substances that are non-malleable and non-ductile.
- Non-malleable substances cannot be shaped into sheets, and non-ductile substances cannot be drawn into wires.

4. **Conclusion**:
- The substances that are generally non-malleable and non-ductile are non-metals. Non-metals do not exhibit these properties, meaning they cannot be easily shaped or stretched.

5. **Final Answer**:
- Non-metals are generally non-malleable and non-ductile.

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