challenge: What was the original plan for the Allied forces after capturing the fortress of Douai in 1710?
  
  A. To invest Béthune and break through the frontière de fer
  B. To invest Cambrai as the next fortress on the way to Paris
  C. To invest Aire and await reinforcements from the Netherlands
  D. To invest Arras and engage the French army in an open battle
  Answer: 