Explanation:

Hardware refers to the physical components of a computer system. This includes not only external input/output devices but also the internal components that perform processing, storage, and communication. Option (a) 'all devices used to input data into a computer' is too narrow, as it only covers input devices and excludes output, processing, and storage components. Option (b) 'sets of instructions that a computer runs or executes' describes software, not hardware. Option (c) 'the computer and all the devices connected to it that are used to input and output data' is better but still incomplete, as it focuses only on I/O and doesn't explicitly mention the core processing and storage units. Option (d) 'all devices involved in processing information including the central processing unit, memory and storage' provides the most comprehensive and accurate definition, encompassing the CPU (for processing), memory (for temporary data storage and access), and permanent storage devices (like hard drives/SSDs), along with other physical components. This option correctly identifies the breadth of what constitutes computer hardware.