challenge: What led to the development and adoption of the .45 ACP M1911 semi-automatic pistol in the US military?
  
  A. The introduction of new rifle technology
  B. The signing of a peace treaty with the Moro Muslims
  C. The surrender of the Moro Rebellion leaders
  D. The phase-out of the .38 caliber Colt M1892 revolver
  Answer: 