What is a command ordered by the court that requires a witness to provide testimony?

The correct answer highlights a legal order specifically aimed at compelling a witness to appear and provide testimony in a legal proceeding. A subpoena testificandum is a type of subpoena that directly requests a witness to testify, either in person or through sworn statements, during a trial or legal proceeding. This is essential for gathering evidence and ensuring that all parties have the opportunity to present witness accounts in court.

Subpoena duces tecum, while also a type of subpoena, specifically requires the production of documents or evidence rather than testimony. Writ of mandamus is a court order compelling a government official to perform a duty that is required by law and is not related to obtaining witness testimony. Judicial notice involves the court recognizing certain facts as true without needing formal evidence, which again does not pertain to a witness providing testimony.

By understanding these distinctions, it becomes clear why subpoena testificandum is the appropriate choice when the question pertains specifically to a court's command for witness testimony.