The correct answer among the choices provided is the fourth option. Personal testimony was used by the speaker to prove his point. The speaker talked about his experiences on how Britain tried to stop the war in Europe. He is credible since he was a Cabinet member during that time.
The action of a play is generally confined to a "world" of its own—that is, to a fictional universe that contains all the characters and events of the play—and none of the characters or actions moves outside the orbit of that world.