Hello. You did not say what text this question refers to. That way it is impossible to answer your question. However, I will help you by showing you what "mood" is within a narrative and showing you how to recognize a change in mood within the story.
When you read a story, you realize that the narrative conveys a kind of emotion, through the narration of the facts and through the actions of the characters. The emotion being conveyed is the mood of the narrative. Often, this mood changes during reading, this change can be gradual or drastic, in addition to showing similar or completely different emotions.
Books with sad and melancholy stories convey an equally sad emotion. That way we can say that the narrative has a sad mood. However, over time the characters begin to change and begin to win their battles and be happy. In this way, the narrative begins to change to a happy mood, for example.
