challenge: How have documented cases of Vancomycin-resistant Staphylococcus aureus (VRSA) typically acquired resistance?
  
  A. Via horizontal gene transfer from other Staphylococcus species
  B. Through spontaneous mutation of the Staphylococcus aureus genome
  C. By uptake of a vancomycin resistance gene cluster from Enterococcus
  D. Through exposure to vancomycin in the environment
  Answer: 