**Core Concept**
The exchange of trace evidence between individuals occurs due to the transfer of particles, fluids, or other substances from one person to another through physical contact. This process is a fundamental principle in forensic science, particularly in the analysis of fingerprints, DNA, and other biological evidence.

**Why the Correct Answer is Right**
When two individuals come into contact, they exchange trace evidence through various mechanisms, including direct contact, indirect contact, and airborne transmission. This exchange can occur through skin-to-skin contact, shaking hands, touching surfaces, or even through airborne particles. The transfer of trace evidence can be influenced by factors such as the duration of contact, the surface area of contact, and the type of substance being transferred.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is not relevant to the exchange of trace evidence between individuals.
* **Option B:** This option is incorrect because it refers to a different principle, not related to the exchange of trace evidence.
* **Option D:** This option is incorrect because it refers to a principle related to the analysis of evidence, not the exchange of trace evidence itself.

**Clinical Pearl / High-Yield Fact**
In forensic science, the exchange of trace evidence can be used to link individuals to crime scenes or other locations, making it a crucial principle in the investigation and prosecution of crimes.

**Correct Answer: C. Contact Transfer**