Which of the following is a protection mechanism of a trusted operating system?

Memory protection is a fundamental mechanism in trusted operating systems, designed to prevent one process from accessing the memory space of another process. This isolation is crucial for ensuring that processes do not interfere with one another, which could lead to unauthorized data access or corruption of memory. In a trusted operating system, this mechanism is enforced rigorously to maintain confidentiality and integrity of processes. By assigning memory areas to processes and ensuring that they can only access their designated spaces, memory protection helps create a secure environment where only authorized users and processes can operate.

The other mechanisms mentioned, while relevant in different contexts, do not specifically align with the established protections of trusted operating systems. Hardware protection might refer to physical measures to secure devices, but it isn't specifically a protection mechanism enforced by the operating system itself. Complete protection and warranty protection are terms that do not accurately describe the operational security measures employed in the context of trusted operating systems. Therefore, memory protection stands out as the correct choice when considering the specific mechanisms that contribute to the security of a trusted operating system.