**Core Concept**
A fixed partial denture (FPD) is a dental restoration that replaces missing teeth and is permanently fixed to adjacent teeth. There are different types of FPDs, including cast metal, ceramic, and composite resin restorations. In this case, the term "Arch-fixed" refers to a specific type of FPD that is fixed within a single arch of teeth.

**Why the Correct Answer is Right**
An arch-fixed partial denture is a type of FPD that is designed to replace missing teeth within a single arch (either the upper or lower jaw). This type of restoration is typically used when there is a significant amount of tooth loss or when the remaining teeth are not sufficient to support a removable partial denture. The arch-fixed FPD is usually constructed using cast metal or ceramic materials and is cemented or bonded to the adjacent teeth to provide stable support.

**Why Each Wrong Option is Incorrect**
**Option A:** This option does not provide any information about the type of FPD being described.
**Option B:** A removable partial denture (RPD) is a type of dental restoration that can be taken out of the mouth, whereas an arch-fixed FPD is permanently fixed in place.
**Option C:** This option does not accurately describe the characteristics of an arch-fixed FPD.

**Clinical Pearl / High-Yield Fact**
When designing an arch-fixed partial denture, it's essential to consider the distribution of forces and the occlusal scheme to ensure that the restoration is stable and functional. A well-designed arch-fixed FPD can provide years of reliable service and improve the patient's quality of life.

**Correct Answer:** C. A fixed partial denture that replaces missing teeth within a single arch (either the upper or lower jaw).