In which type of memory management does the operating system divide physical memory into fixed-size blocks? 

Paging is a memory management technique in which the operating system divides physical memory into fixed-size blocks called pages. Each process is divided into pages of the same size, and these pages are mapped onto frames in physical memory. Paging eliminates the need for contiguous allocation of physical memory and helps avoid issues like external fragmentation. It provides better utilization of memory and allows processes to be loaded into any available frame, making it an efficient method for managing memory in modern operating systems. Option A (Segmentation) is incorrect because segmentation divides memory into variable-sized segments, not fixed-size pages. Option B (Swapping) is incorrect because swapping refers to moving entire processes in and out of memory, not dividing memory into fixed-size blocks. Option D (Contiguous Allocation) is incorrect because this method requires the entire process to be stored in a contiguous block of memory, unlike paging. Option E (Fragmentation) is incorrect because fragmentation is a problem that occurs due to inefficient memory allocation, not a memory management technique itself.