Final answer:
MPLS is an example of a public WAN, being a technique for telecommunications networks that streamlines data routing through short path labels.
Step-by-step explanation:
Among the options provided, MPLS (Multi-Protocol Label Switching) is an example of a public WAN (Wide Area Network). MPLS is a type of data-carrying technique for high-performance telecommunications networks. It directs data from one node to the next based on short path labels rather than long network addresses, avoiding complex lookups in a routing table. This is generally used by service providers to deliver services for multiple customers over a shared network infrastructure.
Other options such as leased lines can be either public or private, while cable internet is a type of internet service to end users, but not classified as a WAN itself. Ethernet is a network protocol that operates primarily within LANs (Local Area Networks), and 'Wans' likely refers to WANs in general, not providing a specific example of a public WAN technology.