Which system component ensures that processes do not access each other's memory spaces?

The correct choice highlights the pivotal role of main memory in ensuring process isolation within an operating system. Main memory, or RAM, is structured in a way that allocates separate memory spaces to different processes. This separation is crucial for maintaining security and stability in an operating system.

When a process is executed, it is assigned a unique address space within main memory. The operating system enforces this separation using memory management techniques, such as paging or segmentation. This prevents one process from accessing or modifying the memory contents of another process, thereby protecting the integrity of data and preventing unauthorized actions or crashes.

By maintaining strict boundaries between these memory spaces, the operating system can ensure that malicious or faulty processes do not interfere with one another, contributing to overall system security and robustness. Thus, the role of main memory is foundational in facilitating secure and efficient process management.