Which of the following protocols is NOT part of the Process/Application layer?

The correct choice is based on the understanding of the OSI (Open Systems Interconnection) model, where the Process/Application layer pertains to protocols that are designed for end-user services and application communication.

TCP, or Transmission Control Protocol, operates at the Transport layer of the OSI model. Its primary function is to provide reliable transport of data between devices on a network, ensuring that packets are delivered in the correct order and without errors. This places TCP outside the realm of the Process/Application layer, which encompasses higher-level protocols tailored for specific applications, such as HTTP (Hypertext Transfer Protocol), IMAP (Internet Message Access Protocol), and SMTP (Simple Mail Transfer Protocol). These protocols focus on facilitating specific tasks like web browsing, email retrieval, and sending emails, characterizing their placement within the Process/Application layer.

Understanding the distinction between the layers is key to recognizing the role each protocol plays in networking. Since TCP is fundamental to data transport rather than application-level tasks, it is appropriately categorized in the Transport layer, confirming the identification of it as the correct answer to the question.