**Core Concept**
The shape of a stab wound is determined by the angle and trajectory of the penetrating object, as well as the properties of the skin and underlying tissues. The wound shape can provide valuable information about the mechanism of injury and can aid in forensic investigation.

**Why the Correct Answer is Right**
The shape of a stab wound is influenced by the angle of penetration, with wounds entering at a shallow angle typically appearing more oval or elliptical, while those entering at a steeper angle may appear more linear or slit-like. This is due to the anisotropic properties of skin, which is more resistant to tearing in one direction than another. The shape of the wound can also be affected by the presence of underlying tissues, such as muscle or bone, which can cause the wound to become more irregular.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because the shape of a stab wound is not solely determined by the type of object used to inflict the injury. While the shape and size of the object may influence the wound shape to some extent, it is not the primary factor.
* **Option B:** This option is incorrect because the location of the wound on the body is not a primary determinant of its shape. While wounds on certain areas of the body, such as the face or neck, may be more prone to specific types of injury, the shape of the wound is not directly related to its location.
* **Option C:** This option is incorrect because the force used to inflict the injury is not the primary factor in determining the shape of a stab wound. While a greater force may result in a larger or more complex wound, the shape of the wound is more closely related to the angle and trajectory of the penetrating object.

**Clinical Pearl / High-Yield Fact**
A key point to remember when examining stab wounds is that the shape of the wound can provide valuable information about the mechanism of injury, even in the absence of other evidence. By carefully examining the wound shape and taking into account the properties of the skin and underlying tissues, forensic investigators can often reconstruct the events surrounding the injury.

**Correct Answer: C. Angle of penetration.**