What is the main duality highlighted between subnetting and supernetting?

• A
  Subnetting converts bits of Host-ID into Net-ID, while supernetting does the opposite.
• B
  Subnetting and supernetting involve only classful addressing.
• C
  Subnetting is used for larger networks while supernetting is for smaller ones.
• D
  Subnetting allows more hosts per network compared to supernetting.