**Core Concept**
The question is testing the understanding of the effects of partial dentures on abutment teeth. In the context of removable partial dentures (RPDs), the distribution of forces and stresses on abutment teeth is a critical consideration. The ideal RPD design aims to minimize the impact on the abutment teeth, ensuring their longevity and preventing potential complications.

**Why the Correct Answer is Right**
The correct answer involves the concept of stress distribution and the role of the **residual ridge** in partial denture wearers. The residual ridge is the bony tissue that remains after tooth loss. In a cast partial denture wearer, the **residual ridge** helps to distribute the forces away from the abutment teeth, thereby reducing the stresses transferred to them. This is achieved through the design of the denture, which includes a **residual ridge**-contouring component that helps to redistribute the forces.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because it does not accurately describe the relationship between the cast partial denture and the stresses transferred to abutment teeth. The cast partial denture does not necessarily increase the stresses on abutment teeth.
* **Option B:** This option is incorrect because it does not address the specific mechanism by which the cast partial denture reduces stresses on abutment teeth. The residual ridge plays a crucial role in this process.
* **Option D:** This option is incorrect because it does not accurately describe the effect of the cast partial denture on abutment teeth. The cast partial denture is designed to reduce stresses on abutment teeth, not increase them.

**Clinical Pearl / High-Yield Fact**
When designing a removable partial denture, it is essential to consider the distribution of forces on the abutment teeth. A well-designed RPD can help to reduce the stresses on abutment teeth, ensuring their longevity and preventing potential complications.

**Correct Answer:** C.