What document serves to inform a defendant of a lawsuit and the court's jurisdiction?

The correct choice is the summons, as it is specifically designed to notify a defendant that a lawsuit has been filed against them. The summons includes essential details such as the plaintiff's identity, the nature of the legal action, and instructions on how the defendant should proceed. It also outlines the court's jurisdiction, informing the defendant where the case is being heard and the legal basis for the court's authority over the matter.

Understanding the role of the summons is crucial in legal procedures, as it initiates the defendant's responsibility to respond to the complaint within a specified timeframe. It ensures that the defendant is aware of the legal proceedings and has an opportunity to prepare a defense. In contrast, other documents like the complaint initiate the action by outlining the plaintiff's claims, while an answer is the defendant's formal response to the complaint. A subpoena, on the other hand, compels a person to appear in court or produce documents, and does not serve the purpose of informing a defendant about a lawsuit.