Final answer:
Chapter 21 of TC 21-305-20 likely covers a specific topic within the manual related to non-tactical vehicle operations for the U.S. Army, such as vehicle operation, maintenance, or safety protocols.
Step-by-step explanation:
The request for information on chapter 21 of TC 21-305-20 refers to a specific section of a military field manual used by the United States Army. This technical manual, titled TC 21-305-20, is dedicated to training programs for non-tactical vehicle operators. While an open-source version of this manual may not be readily available due to its potentially sensitive nature, typically, each chapter of such a manual would cover different aspects of vehicle operation, maintenance, safety protocols, or driving techniques.