Explanation:

Word processing software is designed for creating, editing, formatting, and printing text-based documents. MS-Word (Microsoft Word) is the most ubiquitous and widely used word processing application today, offering extensive features for document creation. Option (b) "WordStar" was also a very popular and influential word processor in the early days of personal computing. However, option (a) "Pagemaker" is primarily desktop publishing (DTP) software, focused on page layout and graphic design, rather than general word processing, although it includes text handling capabilities. Since Pagemaker is not a word processor, option (d) "All" is incorrect. Given that MS-Word is the dominant and most representative example of word processing software among the choices, it is the best answer.