Answer:
Dialogue that reveals background information.
Step-by-step explanation:
"The Miracle Worker" is about Helen Keller and how she overcomes her disabilities through the help of her teacher Miss Annie Sullivan. The story mainly revolves around the character of Annie Sullivan and her struggles trying to help Helen to learn things despite her physical disabilities of being blind and deaf.
In the given excerpt, the author presents the dialogue of Anagnos telling Annie the many obstacles that they had endured and overcome with her when she first came to their school. And in this recollection of how difficult it was also for Annie and the accomplishment that she had achieved, the play presents or uses the dialogue to reveal or provide a piece of background information about Annie.
Thus, the correct answer is the last/ fourth option.