The correct answer is A. Buffer.
A buffer is a temporary storage location that holds data while it is being transferred from one device to another. This can be useful for a variety of reasons, such as to ensure that data is not lost if there is a temporary interruption in the transfer, or to allow multiple devices to access the same data at the same time.
Memory is a more general term that refers to any device that can store data. This can include buffers, but it can also include other types of storage, such as RAM, ROM, and hard drives.
A CPU is the central processing unit of a computer. It is responsible for carrying out the instructions that make up a computer program.
A register is a small amount of high-speed memory that is used by the CPU to store data and instructions.
None of the above is not a correct answer.