Explanation:

Among the given options, a Super computer ($ \text{b} $) is unequivocally the fastest type of computer. Supercomputers are designed for extreme computational power, capable of performing trillions of operations per second (teraflops or petaflops), far exceeding the capabilities of other categories. (a) Mini computers are mid-range systems. (c) Micro computers (personal computers) are for individual use. (d) Mainframes are powerful, high-volume transaction processors but are optimized for reliability and throughput rather than raw speed for single complex tasks like supercomputers. Therefore, Super computer is the fastest.