The Compulsory Process Clause Guarantees the Defendant's Right to Compel

The Compulsory Process Clause guarantees the defendant's right to compel the attendance of favorable witnesses at trial.To compel a person to appear by using a summons,the person to be summoned:

A) must be within the United States, a U.S. territory, or in a nation with an existing treaty with the United States.
B) must be within the United States or a territory of the United States.
C) must be within the United States.
D) must be within the geographical area subject to a court's subpoena power.