challenge: Where is the Loening OA-1A 'San Francisco' currently on display?
  
  A. Smithsonian Institution in Washington D.C.
  B. National Air and Space Museum in Washington D.C.
  C. Steven F. Udvar-Hazy Center of the National Air and Space Museum in Chantilly, Virginia
  D. National Museum of the United States Air Force in Dayton, Ohio
  Answer: 