How does an operating system manage memory allocation?

An operating system manages memory allocation by dividing memory into blocks and assigning them as needed. This approach allows the system to efficiently utilize memory by enabling it to allocate specific portions for different processes based on their requirements.

When a process requests memory, the operating system can quickly assign the necessary blocks, ensuring that each application has the resources it needs to function properly without wasting memory. This block-based method also facilitates effective memory management strategies such as paging and segmentation, allowing for better handling of processes and optimization of system resources.

In contrast, the other options do not reflect efficient memory management. Assigning all memory to a single process would lead to resource contention and deny access to other applications. Reserving memory only for applications does not account for the system's operational needs and can lead to inefficient usage of available resources. Constantly reallocating memory every minute could cause unnecessary overhead and instability, as processes may not be able to access the memory they require when they need it. Thus, the chosen answer highlights a structured and effective approach to memory management in operating systems.