Answer:
The correct answer is D, "So that the listener is already familiar with the themes as the story unfolds."
Step-by-step explanation:
The main themes introduced in the overture serve as musical introductions to the characters, storylines, and moods that will be present in the play or opera. By presenting these themes in the overture, the composer aims to prepare the listener for the musical and emotional journey that is about to unfold, and to set the tone for the performance. By the time the actual performance begins, the listener should already be familiar with the themes and able to recognize them as the story progresses.