Given the task definition and input, reply with output. This task is about writing a correct answer for the reading comprehension task. Based on the information provided in a given passage, you should identify the shortest continuous text span from the passage that serves as an answer to the given question. Avoid answers that are incorrect or provides incomplete justification for the question.

Passage: The novel has been noted for its poignant exploration of different forms of courage. Scout's impulsive inclination to fight students who insult Atticus reflects her attempt to stand up for him and defend him. Atticus is the moral center of the novel, however, and he teaches Jem one of the most significant lessons of courage. In a statement that foreshadows Atticus' motivation for defending Tom Robinson and describes Mrs. Dubose, who is determined to break herself of a morphine addiction, Atticus tells Jem that courage is "when you're licked before you begin but you begin anyway and you see it through no matter what". Question: Mrs. Dubose suffers from an addiction to what?
morphine