The correct answer is: A. processor and memory.
A memory bus is a data pathway that allows the processor to communicate with the main memory. It is a high-speed connection that allows the processor to read and write data to memory. The memory bus is typically made up of multiple parallel lines, each of which carries a different bit of data. The number of lines in the memory bus determines the maximum amount of data that can be transferred at any given time.
The memory bus is a critical component of the computer system. Without it, the processor would not be able to access memory and would not be able to run programs.
Option B is incorrect because the processor communicates with I/O devices through a separate bus called the I/O bus.
Option C is incorrect because I/O devices communicate with memory through the memory bus.
Option D is incorrect because input devices and output devices do not communicate with each other directly. They communicate with the processor, which then communicates with the appropriate device.
Option E is incorrect because the memory bus is used for communication between the processor and memory.