Final answer:
Tunneling is the process where tunnels are used to connect multiple sites on a WAN, often creating a secure virtual private network by encapsulating encrypted data packets for transmission.
Step-by-step explanation:
When tunnels connect multiple sites on a WAN, that process is known as c. Tunneling. Tunneling is a method where encrypted data packets are encapsulated within other packets to create a secure connection across a public network, such as the internet. This is done to ensure that data can be transmitted securely from one site to another within a Wide Area Network (WAN), making it appear as though the sites are directly connected, despite being geographically distant. By using a tunneling protocol such as IPsec or SSL/TLS, a virtual private network (VPN) is often created, enabling secure communication between sites.