Step 1: Understanding WAN.
A WAN (Wide Area Network) is a telecommunications network that extends over a large geographical area, such as a city, country, or even globally.
Step 2: Evaluate each option.
- Option (1) PAN: A PAN (Personal Area Network) is a small network, usually limited to a small area like a room or personal workspace.
- Option (2) WWW: The WWW (World Wide Web) is a system of interlinked hypertext documents but not a network.
- Option (3) Ethernet: Ethernet is a protocol for local area networks (LANs), not a WAN.
- Option (4) Internet: The Internet is the largest WAN that connects billions of devices globally.
Step 3: Conclusion.
The correct answer is the Internet, as it is the largest WAN connecting devices globally.
Final Answer:
\[
\boxed{\text{The largest WAN is the Internet.}}
\]