Explanation:

This question reiterates the fundamental operational principle of computers. Option (a) 'processing' describes the *action* computers perform on data, not the *system* they use for data representation. Option (b) 'kilobyte' is a unit of data storage, not a system for processing data. Option (c) 'binary' refers to the binary number system, which is the system computers fundamentally use to represent and process all data. Every piece of information, from text to images to program instructions, is encoded as a sequence of $0$s and $1$s. This is the correct answer. Option (d) 'representational' is too vague and not a specific system. Option (e) 'none of these' is incorrect as option (c) accurately describes the system used.