What is true regarding a default route?

A.
The default route is always used first. When the default route is not available more specific routes are tried.

B.
When a default route is set, all other routes are disabled until the default route is deleted.

C.
The default route is only used if there is not a more specific route to a destination host or network.

D.
Without a default route, no network communication even in directly attached networks is possible.