**Core Concept**
The question pertains to the specification of K-type endodontic files, specifically the rate of increase in file diameter as a function of length, as per the American Dental Association (ADA) Specification No. 28. This specification outlines the dimensional requirements for endodontic files to ensure their safety and effectiveness in root canal procedures.

**Why the Correct Answer is Right**
The correct answer reflects the precise rate of increase in file diameter per running millimeter of length, as defined by the ADA Specification No. 28. From point D0 to point D16, the file diameter increases at a rate of 0.02 mm per millimeter of length. This rate is critical for maintaining the desired apical transportation and ensuring the optimal shape of the root canal. The precise dimensional control is essential for preventing file breakage and ensuring the effective removal of infected pulp tissue.

**Why Each Wrong Option is Incorrect**
**Option A:** 0.01 mm/mm is incorrect because it represents a lower rate of increase than specified by the ADA, which could lead to inadequate apical transportation and incomplete canal preparation.
**Option B:** 0.03 mm/mm is incorrect because it represents a higher rate of increase than specified by the ADA, which could lead to excessive apical transportation and canal transportation beyond the desired shape.
**Option C:** 0.04 mm/mm is incorrect because it represents an even higher rate of increase than option B, which would likely result in significant apical transportation and file breakage.

**Clinical Pearl / High-Yield Fact**
When using endodontic files, it is essential to adhere to the specifications outlined by the ADA to ensure the optimal shape of the root canal and prevent file breakage. Familiarize yourself with the dimensional requirements for different types of files to avoid common mistakes and improve patient outcomes.

**Correct Answer:** 0.02 mm/mm. The rate of increase in file diameter per running millimeter of length for a K-type file from point D0 to point D16 is 0.02 mm/mm.