Which term means to reason with someone in an effort to dissuade them?

The term "expostulate" is defined as to reason earnestly with someone in an effort to dissuade them from an action or decision they are considering. It implies a conversation where one party expresses doubts or objections to the other's intentions, often with the aim of persuading them to reconsider. This word is commonly used in contexts where persuasion through rational discussion is attempted, making it the best fit for the meaning sought in the question.

In contrast, "exscind" means to cut out or remove something, which does not relate to reasoning or persuasion. "Effluvia" refers to unpleasant or harmful odors or fumes, showing no connection to the act of reasoning or persuading. "Encomium" is a term used to describe a formal expression of praise, which is also unrelated to the action of dissuading someone through reasoning. Thus, "expostulate" stands out as the correct answer due to its specific connotation of reasoning in an effort to change someone’s mind.