Explanation:

The Central Processing Unit (CPU) consists of several key components, and the 'ALU' (Arithmetic Logic Unit) is one of its fundamental parts. Option (d) 'ALU' is responsible for performing all arithmetic and logical operations. Options (a) 'Key board', (b) 'Printer', and (c) 'Tape' are all peripheral devices used for input, output, or storage, respectively, and are external to the CPU. Therefore, the ALU is the only component listed that is an integral part of the CPU.