Concept: The central working system of a computer is the component where data and instructions are held while processing takes place.
Explanation:Computers need a place to store data temporarily before and during processing.
The monitor is only an output device for displaying information.
The floppy disk drive and hard drive are secondary storage devices used for saving files permanently.
The memory unit, also called main memory or primary storage, is located within the system unit.
It supplies the processor with the instructions and data needed for data processing.
Therefore, among the options given, the memory unit is the central working system of the computer.
Answer: A. memory unit