challenge: When did the Royal Air Force (RAF) consider the Battle of Britain to have officially taken place?
  
  A. 10 July 1940 - 31 October 1940
  B. 1 September 1940 - 30 November 1940
  C. 10 June 1940 - 31 August 1940
  D. 1 January 1941 - 31 March 1941
  Answer: 