Explanation:

The correct answer is (c) program. Software is a general term that encompasses all programs, data, and instructions that tell a computer what to do. At its core, software is fundamentally composed of one or more programs, which are sequences of instructions designed to perform specific tasks. Therefore, 'program' is the closest and most appropriate synonym among the given options for the executable components of software. (a) Input refers to data or signals fed into a computer for processing. It is not synonymous with software itself, but rather something software processes or receives. (b) Output refers to the results produced by a computer after processing input. It is the outcome of software execution, not the software itself. (d) A system is a broader concept that includes an integrated collection of components working together, typically comprising hardware, software, data, people, and processes. While software is a crucial part of a computer system, 'system' is not a synonym for just 'software'. (e) None of these is incorrect, as option (c) serves as a strong synonym for the functional essence of software.