**Core Concept**
The C-factor is a measure of the confinement of a restoration to the tooth structure, which affects the flow of fluid and the diffusion of ions during the restoration process. In the context of composite restorations, the C-factor is particularly relevant for class IV restorations, where the restoration is confined to a small area and may not allow for adequate fluid flow.

**Why the Correct Answer is Right**
The C-factor is calculated as the ratio of the bonded surface area to the total surface area of the restoration. For a class IV composite restoration, the bonded surface area is the area in contact with the tooth structure, while the total surface area includes both the bonded and unbonded areas. A higher C-factor indicates a more confined restoration, which can lead to increased polymerization shrinkage stress and decreased marginal integrity. The C-factor for a class IV composite restoration is typically around 2, indicating a moderate level of confinement.

**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because it would indicate a low level of confinement, which is not typical for a class IV composite restoration.
**Option B:** Incorrect because it would indicate a high level of confinement, which could lead to increased polymerization shrinkage stress and decreased marginal integrity.
**Option C:** Incorrect because it is not a valid value for the C-factor, which is typically a ratio between 1 and 3.

**Clinical Pearl / High-Yield Fact**
Remember that the C-factor is a critical factor in determining the success of composite restorations, particularly for class IV restorations. A higher C-factor can lead to increased polymerization shrinkage stress and decreased marginal integrity, which can compromise the longevity of the restoration.

**Correct Answer: C. 2**