The correct definition of mood from your options is:
The mood is the atmosphere or feeling created, established through descriptive language and setting.
Mood refers to the emotional quality or atmosphere that a reader experiences while engaging with a text. It is typically established through various literary techniques, including the use of descriptive language, imagery, tone, and setting. For example, dark or gloomy descriptions can create a somber mood, while bright and cheerful language may evoke a more uplifting mood.
Although dialogue can also influence the mood, it is mainly the descriptive elements that play the primary role in creating the overall feeling of the text.