challenge: What can be gathered about the wartime structure of NORTHAG in the autumn of 1989?
  
  A. It was only available through declassified documents after the fall of the Soviet Union
  B. It was completely classified and not publicly available
  C. It can be pieced together from multiple public sources, but may be inconsistent and/or incomplete
  D. It was publicly disclosed in a single source document
  Answer: 