To answer this question, we need to understand the concept of metrics in routing protocols.
Option A) A metric is the administrative distance of a routing protocol - This option is incorrect. The administrative distance is a concept used in routing to determine the preferability of routes from different routing protocols. It is not the same as a metric, which is a value used to measure the desirability of a route.
Option B) A metric is a measure of trustworthiness and availability of a route - This option is correct. In routing protocols, a metric is a value assigned to a route to represent its desirability. It can be based on various factors such as bandwidth, delay, reliability, or cost. A lower metric typically indicates a more preferred route.
Option C) Both of the above - This option is incorrect. Option A is incorrect, as explained above.
Option D) None of the above - This option is incorrect. Option B is correct, as explained above.
The correct answer is B. This option is correct because a metric in routing protocols is a measure of trustworthiness and availability of a route.