Which staging effect is used in the Utah Valley University production of The Tempest

C. Character voices coming from offstage.
Explanation:
William Shakespeare's play "The Tempest" tells the story of a king and his men shipwrecked in an island under the influence of magic art by Prospero, a banished king. And the prince Ferdinand falling in love with Ariel, Prospero's daughter.
Utah Valley University staged a production of this play, which succeeded immensely. The director Christopher Clark used only male actors, following in the ways of Shakespeare's times. The four 'narrators/ voices' sat under the stage and gave a perfect individual voice qualities to their respective characters, full on with vivid descriptions, voice expressions and wonderful nuances. The whole production of this play succeeded mainly because of these amazing actors, the character voices from offstage.