**Core Concept**
Fingerprints are unique patterns of ridges and valleys found on the fingertips, used for identification purposes. The formation of fingerprints is a complex process involving the interaction of genetic and environmental factors.

**Why the Correct Answer is Right**
The correct answer is related to the unique characteristics of fingerprints. Fingerprints are formed by the interaction of the dermal papillae and the epidermal ridges. The dermal papillae are small projections of the dermis that penetrate the epidermis, and the epidermal ridges are the raised patterns on the surface of the skin. The combination of these structures gives rise to the unique patterns found in fingerprints.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because fingerprints are indeed found on the fingertips, making it a distractor.
**Option B:** This option is incorrect because fingerprints are unique to each individual, and their patterns are not seen in any other part of the body.

**Clinical Pearl / High-Yield Fact**
The uniqueness of fingerprints makes them an effective tool for identification purposes. It's essential to remember that fingerprints are formed by the interaction of genetic and environmental factors, making them a complex and unique feature of the human body.

**Correct Answer: D. Palm or sole.**