A mainframe is a very powerful multi-user computer that can support thousands of users at the same time. A server is similar to a mainframe that serve many uses with the main difference that the users (called clients) usually do their own processing. A minicomputer is a multi-user computer that supports hundreds of users simultaneously. Microcomputer is also called as personal computer (PC). PC is usually used by single person at home, Office and business environments. Nowadays, it is the most common type of computer. PC can be in the form of desktop, laptop or tablet form. A supercomputer is an extremely fast computer that can perform hundreds of millions of instructions (or more) per second using parallel processing. They are often used for very complex calculations in science and engineering problems. The correct answer is Choice D.