What does administrative distance refer to?

A.
the cost of a link between two neighboring routers

B.
the advertised cost to reach a network

C.
the cost to reach a network that is administratively set

D.
a measure of the trustworthiness of a routing information source

Explanation:
http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a0080094195.shtml
Administrative distance is the feature that routers use in order to select the best path when there
are two or more different routes to the same destination from two different routing protocols.
Administrative distance defines the reliability of a routing protocol. Each routing protocol is
prioritized in order of most to least reliable (believable) with the help of an administrative distance
value.
Administrative distance is the first criterion that a router uses to determine which routing protocol
to use if two protocols provide route information for the same destination. Administrative distance
is a measure of the trustworthiness of the source of the routing information. The smaller the
administrative distance value, the more reliable the protocol.