**Core Concept**
The retentive points in a class II cavity are placed to provide additional retention to the restoration, especially in areas with high occlusal forces. This is crucial in preventing the restoration from dislodging or loosening over time.

**Why the Correct Answer is Right**
The retentive points are typically placed on the proximal box walls or on the proximal surfaces of the tooth, utilizing the inherent anatomy of the tooth to create a mechanical retention. This is achieved by using a small drill to create a small depression or a notch on the surface, allowing the restorative material to flow into and bond with the tooth structure. This provides a strong mechanical lock that enhances the retention of the restoration.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect as retentive points are not typically placed on the occlusal surface, as it is not an effective location for mechanical retention.
* **Option B:** This option is incorrect as retentive points are not typically placed on the lingual or labial surfaces of the tooth, as these areas do not provide sufficient mechanical retention.
* **Option C:** This option is incorrect as retentive points are not typically placed on the incisal edge of the tooth, as it is not a suitable location for mechanical retention.

**Clinical Pearl / High-Yield Fact**
When placing retentive points, it is essential to use a small drill and to create a small depression or notch on the surface, allowing the restorative material to flow into and bond with the tooth structure.

**Correct Answer:** C.