- A) Micro-controller

A micro-computer is defined as a complete computing system built around one or more microprocessors as its CPU core. It integrates multiple microprocessors along with memory, I/O interfaces, and other components on a single platform. Micro-controller is a single-chip system with limited processing, micro-processor is the CPU itself (not a collection of them), and micro-transistor is a component, not a computer system.

Step-by-step Derivation:
The question asks what system is defined by having 'a number of microprocessors at its CPU'. Breaking down the terminology: A micro-computer is a small-scale computing system that uses microprocessor(s) as its central processing unit. While a single micro-computer typically has one main microprocessor, the definition encompasses systems that can have multiple processing elements. A micro-controller integrates the CPU, memory, and I/O on one chip for embedded applications. A microprocessor is the CPU component itself, not a system containing multiple of them. A micro-transistor is a basic electronic component. Therefore, the system described as having microprocessors as its CPU is a micro-computer.