challenge: What makes the Velvet Underground acetate record put up for auction by Shuga Records in 2014 extremely rare?
  
  A. Only two copies of the record are known to exist
  B. It is signed by all members of The Velvet Underground
  C. It features early recordings of songs never released by The Velvet Underground
  D. It is the only existing copy of The Velvet Underground & Nico album
  Answer: 