The USConstitution States That the National Government Must "Insure Domestic Tranquility

The U.S.Constitution states that the national government must "insure domestic Tranquility." How does the U.S.government perform that function?

A) It does so through law-enforcement agencies that include the FBI, the National Guard, and the Department of Homeland Security.
B) It does so through military protection provided by the Army, Navy, Marines, Coast Guard, and Air Force.
C) It does so through the system of checks and balances outlined in the U.S. Constitution.
D) It does so through the powers granted to the president of the United States in Article II of the U.S. Constitution.
E) It does so through agencies that include the Justice Department and the State Department.