Where can we still find part of Von Steuben's Blue Book today?

The correct response identifies that part of Von Steuben's Blue Book can be found in TC 3-21.5 Drill and Ceremonies. Von Steuben's Blue Book, formally known as "Regulation for the Order and Discipline of the Troops of the United States," was a key document in shaping military training and discipline in the Continental Army. This manual laid foundational practices that are still relevant today, particularly in the realm of drill and ceremonies.

TC 3-21.5 is explicitly focused on drill and ceremonies within the Army. It reflects historic regulations and practices that can be traced back to Von Steuben's work. This continuity ensures that military formations, movements, and ceremonies are conducted with precision, fostering discipline and unity among soldiers.

The other options do cover various aspects of military training, standards, or regulations, yet they do not specifically focus on drill and ceremonies as comprehensively as TC 3-21.5 does. This makes TC 3-21.5 the most relevant current source for those practices inspired by Von Steuben's Blue Book.