The correct option is D conclusion
Introduction means a thing preliminary to something else, especially an explanatory section at the beginning of a book, report, or speech. The opposite of introduction is conclusion, or the end or finish of an event, process, or text. Hence, Option D is correct. Among the rest of the options, deduction means the action of deducting or subtracting something., end means a final part of something, especially a period of time, an activity, or a story, termination means the act of ending something or the end of something. These options do not express this antonym, hence incorrect.