Final answer:
Channel selection is the correct answer, as it includes specifying all of the communications systems for a project to ensure efficient and effective information sharing.
Step-by-step explanation:
The question 'Which communications management practice includes specifying all of the communications systems?' pertains to the planning processes involved in project management, particularly in the knowledge area of Project Communications Management. The correct answer to this question is c) Channel selection. In project management, channel selection involves determining the methods or technology used to convey messages among project stakeholders. This includes specifying all available communications systems and platforms that are suitable for messages being sent. It is vital for ensuring that information is shared efficiently and effectively throughout the project lifecycle. Other options like encoding and decoding are associated with the actual preparation and interpretation of the message, while feedback is a response to the message.