challenge: What was the primary purpose of constructing the Lines of Torres Vedras, including the Fort of Zambujal, during the Peninsular War?
  
  A. To blockade the port of Ericeira and disrupt French supply lines
  B. To launch a counterattack against the French forces
  C. To protect Lisbon from Napoleon Bonaparte's troops and secure a potential retreat for the British army
  D. To besiege the city of Sintra and capture its strategic location
  Answer: 