The correct answer is: A. addition processor.
An addition processor is a specialized computer chip that can be used to speed up the processing of certain types of calculations. It can be added to a microcomputer to improve its performance in tasks such as graphics processing, video editing, and scientific computing.
Expansion cards are devices that can be added to a microcomputer to provide additional features or functionality. They can be used to add new storage devices, network connections, or input/output devices. However, they do not directly improve the processing capability of the microcomputer.
Secondary memory is a type of storage that is used to store data that is not currently being used by the microcomputer. It is typically slower than main memory, but it has a much larger capacity. Secondary memory can be used to store programs, data files, and other information that needs to be accessed frequently. However, it does not directly improve the processing capability of the microcomputer.
Buffer memory is a type of memory that is used to store data that is being transferred between the microcomputer and other devices. It can help to improve the performance of the microcomputer by reducing the number of times that the microcomputer needs to access the slower secondary memory. However, it does not directly improve the processing capability of the microcomputer.