**Core Concept**
The American Dental Association (ADA) specifications outline the requirements for various dental materials, including those used for repairing denture bases. The specifications ensure that these materials meet specific standards for safety and efficacy.

**Why the Correct Answer is Right**
Chemically activated resins, also known as acrylic resins, are commonly used for repairing denture bases due to their ease of use and acceptable mechanical properties. The ADA specification number for chemically activated resins used in denture base repair applications provides the minimum requirements for the physical, chemical, and biological properties of these resins. This includes requirements for the resin's viscosity, curing time, and biocompatibility. The correct ADA specification number ensures that the resin meets these standards, thereby providing a safe and effective repair material.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not correspond to the ADA specification number for chemically activated resins used in denture base repair applications.
**Option B:** This option is incorrect because it is not a valid ADA specification number for chemically activated resins.
**Option D:** This option is incorrect because it is not a valid ADA specification number for chemically activated resins used in denture base repair applications.

**Clinical Pearl / High-Yield Fact**
It is essential to note that the ADA specification number for chemically activated resins used in denture base repair applications can vary depending on the country and region. Practitioners should always consult the relevant ADA specification and follow the manufacturer's instructions for the specific product being used.

**Correct Answer:** C.