A core business unit relies on an effective legacy system that does not meet the current security standards and threatens the enterprise network. Which of the following is the BEST course of action to address the situation?

A. Document the deficiencies in the risk register.
B. Disconnect the legacy system from the rest of the network.
C. Require that new systems that can meet the standards be implemented.
D. Develop processes to compensate for the deficiencies.