The correct answer is: A. the i/o devices and the memory share the same address space.
In memory-mapped I/O, I/O devices are accessed through the same memory addresses as regular memory locations. This allows the CPU to access I/O devices directly, without the need for special I/O instructions.
Option B is incorrect because I/O devices do not have a separate address space. They share the same address space as regular memory locations.
Option C is incorrect because the memory and I/O devices do not have an associated address space. They share the same address space.
Option D is incorrect because a part of the memory is not specifically set aside for the I/O operation. The I/O devices share the same address space as regular memory locations.