When No Written Contract Exists, Who Chooses an Arbitrator to Resolve

When no written contract exists, who chooses an arbitrator to resolve disputes?

A) The American Arbitration Association
B) The two parties select an arbitrator and the two arbitrators select a third to act.
C) The two parties select an arbitrator and the court decides.
D) The court selects an arbitrator of its choosing.
E) Arbitration