challenge: What was the title of Fritz Kern's major work that reset the compass in the study of Medieval legal and constitutional history?
  
  A. Gottesgnadentum und Widerstandsrecht im früheren Mittelalter
  B. Kingship and law
  C. Comparative Constitutional History of the Middle Ages
  D. The Grace of God and Rights to Resist in the Early Middle Ages
  Answer: 