challenge: What is the location of the true origin of the Irish grid system and the Irish Transverse Mercator system?
  
  A. A point in the River Shannon, near Limerick
  B. A point in the Irish Sea, off the coast of Dublin
  C. A point in Lough Ree, close to the western shore
  D. A point in the Mountains of Mourne, near Belfast
  Answer: 