What is the most important one among the realities listed? [A] New vulnerabilities will be introduced into your environment every day. [B] If employees disregard warnings about the hazards of opening questionable email attachments, the manager should educate them about properly configuring firewalls and intrusion detection systems for their PCs. [C] Managers have more responsibility than ever. [D] Security managers are asked to support increasing degrees of network availability and access.