Read the passage from "The Lady, or the Tiger.” Directly opposite him, on the other side of the inclosed space, were two doors, exactly alike and side by side. It was the duty and the privilege of the person on trial to walk directly to these doors and open one of them. He could open either door he pleased; he was subject to no guidance or influence but that of the aforementioned impartial and incorruptible chance.

What is the author’s purpose for describing the two doors as absolutely identical?
a. to reveal that the outcome of the trial is decided by luck
b. to show that the verdict is predetermined
c. to reveal that the defendants are in control of the verdict
d. to emphasize that the trial is completely fair