An individual is first with the network before they are authorized to access resources on the network A. countermeasure B. vulnerability C. adversary D. risk

Answer:A) Countmeasure

Explanation: Countermeasure is the activity that is used for the reduction or avoidance of the threats or malfunction that occur in the operating system. The tool consists of the major components like firewalls, antiviruses etc to secure the system. It protects the servers, data systems, networks etc.

Other options are incorrect because vulnerability is the capability of a system being in exposed situation, adversary is a conflict situation and risk is the event that can cause loss in the operating system. Thus, the correct option is option (A) for checking the authorization of the individual and then only letting him access the network.