challenge: What was the primary modification made by Mikhail Yevgenyevich Berezin to create the B-20 in 1944?
  
  A. Converting the Berezin UB machine gun to use 20 mm rounds
  B. Converting the Berezin UB machine gun to use 12.7 mm rounds
  C. Increasing the muzzle velocity of the Berezin UB machine gun
  D. Replacing the pneumatic charging system with an electric one
  Answer: 