Which method of discovery allows a defendant to ask direct questions to the plaintiff under oath?

The correct choice is oral deposition because it is a method of discovery where a defendant can question the plaintiff directly, under oath, in a formal setting. During an oral deposition, the opposing party is typically present, and the questions and answers are recorded by a court reporter. This process allows for a dynamic exchange, enabling the defendant to probe for details, clarify responses, and gather information that may be useful for the case.

In contrast, interrogatories involve written questions that one party sends to another, which the receiving party must answer in writing and under oath, but they lack the immediacy and interaction of an oral deposition. A written deposition is not a standard term in legal discovery processes; it may suggest a document-based gathering of testimony, but it does not match the interaction involved in an oral deposition. A request for admissions is a tool used to establish certain facts as uncontested, rather than a method for questioning a party directly.