The Internet is an example of which computer network?

Networks are grouped by the size of the area they cover. A network confined to one building is local; a network that spans cities, countries, or continents, connecting many smaller networks together, is described as "wide" in scope.

The Internet links millions of separate networks across the entire planet, so it fits the definition of a WAN (wide area network): it is the largest possible example of this network class, built from countless smaller networks joined together through routers, undersea cables, and satellite links.

A LAN is too small in scope (one site), and a MAN (metropolitan area network) only covers a city. "CAN" is not a standard, widely recognised network category taught at this level, so it can be set aside.

Remember the size ordering: LAN (building) is smaller than a MAN (city), which is smaller than a WAN (country or world). The Internet always sits at the top of that scale.