Final answer:
The rigid metal that joins the right and left quadrant sides of a partial denture framework is known as the framework. It is essential for structure and support, distributing forces evenly for comfort and function.
Step-by-step explanation:
The component of the partial denture that is a piece of rigid metal that joins the right and left quadrant sides of the framework is the C) Framework. The framework of a partial denture is critical for providing structure and support for the overall dental appliance. It connects the various elements of the partial denture, including clasps, denture bases, and artificial teeth, and is designed to distribute masticatory forces evenly to ensure comfort and functionality.