What purpose do drawbridges serve over navigable waters?

• They serve as fishing docks and scenic walkways.
• They facilitate the movement of vehicular traffic across waterways.
• Drawbridges raise or turn to allow marine traffic to pass underneath.
• Both B & C
  Explanation:

  "Drawbridges are mechanical bridges over navigable waters that facilitate the movement of vehicular traffic across waterways and raise or turn to allow marine traffic to go under them."