Explanation:

The main system board of a computer is known as the motherboard. It is the central printed circuit board (PCB) that connects and allows communication between all crucial electronic components of the system. These components include the Central Processing Unit (CPU), memory (RAM), and various expansion cards. Option (a) 'integrated circuit' (IC) is a tiny electronic circuit, a component found *on* the motherboard, but not the motherboard itself. Option (c) 'processor' (CPU) is the 'brain' of the computer, a single component that is plugged into the motherboard, not the board itself. Option (d) 'microchip' is another term for an integrated circuit, similar to option (a). Thus, 'mother board' (b) is the correct term for the main system board. Option (e) 'None of these' is incorrect as (b) is the accurate term.