The correct answer is MS-Word. MS-Word:Microsoft Word or MS-WORD is a graphical word processing program that users can type with. It allows the users to type and save documents very similar to other word processors. Microsoft Word or MS Word is a graphical word processing program that users can type with. It is made by the computer company Microsoft. Its purpose is to allow users to type and save documents. Similar to other word processors, it has helpful tools to make documents. Since separate options are available for bibliography, table of contents, etc. , it is the best tool that can be used by researchers for writing books, Ph. D. thesis and adjusting it as per the layout and alignment of one's choice. Hence, for the researcher the best software for writing the Ph. D. thesis is MS-Word.