Why does marty sleep on the couch and does he complain?

What are the purposes of a prologue in a play? 1) to provide information about the inner thoughts and feelings of a character 2) to set the mood and tone of the play and provide background information 3) to provide information about how the stage should be set and what props are needed 4) to give some insight into the relationships among different characters 5) to provide a hint to the audience about what will happen later in the play