In personal computer hardware, which one of the following is the main system board that holds the CPU, memory slots, expansion slots and key connectors?

Introduction / Context:
Every personal computer contains a large printed circuit board that serves as the central backbone connecting all major components. This board provides sockets for the processor and memory, slots for expansion cards and connectors for storage devices and external ports. In everyday computer terminology, this main system board has a specific name that exam questions often ask you to recall. Knowing this term helps you talk accurately about upgrades, repairs and system components.

Given Data / Assumptions:

• The question refers to the main system board of a computer.
• This board holds the CPU, RAM slots, expansion slots and connectors.
• Options include CPU, keyboard, microchip, motherboard and power supply unit.
• We assume a standard desktop or laptop PC architecture.

Concept / Approach:
The main system board of a computer is called the motherboard. It is a large printed circuit board containing the CPU socket, memory slots, chipset, expansion slots for graphics and other cards and connectors for power, storage and external ports. The CPU itself is a chip that plugs into the motherboard, not the board as a whole. The keyboard is an input device, and microchip is a generic term for any integrated circuit. The power supply unit converts mains electricity to low voltage power and connects to the motherboard but is not the system board itself. Therefore, the correct answer is motherboard, often referred to as the main system board.

Step-by-Step Solution:

Verification / Alternative check:
Hardware manuals and PC building guides consistently refer to the main board inside a computer case as the motherboard. They show diagrams of the board with labels for RAM slots, chipset, CPU socket and power connectors. The CPU is shown as a separate component that is installed on the motherboard. The term microchip is used generically for integrated circuits of many types, not just for system boards. No reputable source calls the entire main system board a CPU, keyboard or power supply. This consistent usage confirms that motherboard is the correct answer in exam questions about the main system board.

Why Other Options Are Wrong:

• Central Processing Unit (CPU): The CPU is the main processing chip, not the board that connects all components.
• Keyboard: An external input device used for typing, completely separate from the internal system board.
• Microchip: A generic term for integrated circuits; does not specifically refer to the large system board.
• Power supply unit: Converts AC power to DC and feeds the motherboard but is not the motherboard itself.

Common Pitfalls:
Some learners incorrectly say CPU when they mean the whole system unit or system board. This confusion is common in everyday speech but is incorrect in technical contexts. To avoid this, remember that the CPU is just one chip among many on the motherboard. The motherboard is the big board that everything else plugs into. When an exam question mentions the main system board or mainboard, always think of the motherboard as the correct technical term.

Final Answer:
The main system board of a computer is called the Motherboard (main system board).