Task: Question Generation
Input (English):  In Berkeley, California in 1988, Mark O'Brien is a poet who is forced to live in an iron lung due to complications from polio. Due to his condition, he has never had sex. After unsuccessfully proposing to his caretaker Amanda, and sensing he may be near death, he decides he wants to lose his virginity. After consulting his priest, Father Brendan, he gets in touch with Cheryl Cohen-Greene, a professional sex surrogate. She tells him they will have no more than six sessions together. They begin their sessions, but soon it is clear that they are developing romantic feelings for each other. Cheryl's husband, who loves her deeply, fights to suppress his jealousy, at first withholding a love poem that Mark has sent by mail to Cheryl, which she eventually finds. After several attempts, Mark and Cheryl are able to have mutually satisfying sex, but decide to cut the sessions short on account of their burgeoning feelings.
One day sometime later, the power goes out in the building in which Mark lives, causing the iron lung to stop functioning and making it necessary for Mark to be rushed to the hospital. However, he survives and meets Susan Fernbach, a young woman with whom the audience senses he will finally find happiness. The film then cuts to Mark's funeral, held sometime later, and attended by four of the women he came to know and care for, including Cheryl. Father Brendan gives the homily and Susan reads the poem he had previously sent Cheryl.
Output (English): Why do Mark and Cheryl stop their sessions?