challenge: What is the name of the unusually stable oxonium species mentioned in the text?
  
  A. Tetrakis(triphenylphosphinegold(I))oxonium tetrafluoroborate
  B. Tris[triphenylphosphinegold(I)]oxonium tetrafluoroborate
  C. Bis(triphenylphosphinegold(I))oxonium tetrafluoroborate
  D. Pentakis(triphenylphosphinegold(I))oxonium tetrafluoroborate
  Answer: 