Answer:C) Feedback
Step-by-step explanation: System control is the controlling and managing activity of the system by commands ,regulations, management practices etc.It helps in the analyzation of the system and improving the ability of performing the tasks.Feedback is the component of the control system that is obtained as the output after the controlling technique is applied in the system.
Other options are incorrect because environment is the surrounding of the system ,interface is the connection between the components of the system and boundary is not a technical term of control system.Thus, the correct option is option(C).