Explanation:

A computer system is composed of various hardware and software components. (a) Memory (e.g., RAM, ROM, cache) is a fundamental hardware component for storing data and instructions. (c) CPU (Central Processing Unit) is the "brain" of the computer, performing all processing. (d) ALU (Arithmetic Logic Unit) is a core part of the CPU, responsible for arithmetic and logical operations. (b) Paper is a consumable material used for printing output, but it is not an internal or external component of the computer system itself. Therefore, paper is NOT a computer component.