A cloud is an example of:

two computers linked by a flash drive

an unknown network

three computers that share a router

or two computers connected by a cable

I think the answer is C, three computers that share a router.

Three computers that share a router

Explanation:

cloud computing is basically storing and accessing information over the internet via the connection of any device that can access the internet instead of accessing the files using the computer hard drive to access the files. routers are used for the connection of systems like computer to a network usually a n internet network, hence three computers that share a router is automatically been connected to the internet.

computers been linked by a flash drive are connected internally to themselves and not the internet, A cloud is a known network while two computers connected by a cable might not as well be connected to the internet. Google provides such service of cloud computing.