challenge: What is the primary function of the Sperberhai Dyke in the Harz mountains of central Germany?
  
  A. To carry the water of the Dyke Ditch over the depression of the Sperberhai to the Clausthal plateau
  B. To control flooding in the Clausthal plateau
  C. To generate hydroelectric power
  D. To supply water to the nearby towns and villages
  Answer: 