challenge: How are features identified on lunar maps in relation to Crüger?
  
  A. By placing the letter on the side of the crater midpoint that is farthest from Crüger
  B. By placing the letter at the center of the crater
  C. By placing the letter at the edge of the lunar map
  D. By placing the letter on the side of the crater midpoint that is closest to Crüger
  Answer: 