Concept:The memory unit is an internal hardware component that is housed inside the main body of the computer.
Explanation:The system unit is the main casing that holds the internal components of a computer.
These components include the motherboard, central processing unit (CPU), and memory unit.
The memory unit is therefore physically located within the system unit, not inside the control unit or an input/output device.
Control unit is part of the CPU, while input and output devices are external peripherals.
Thus, the memory unit belongs to the system unit.
Answer:D. system unit.