The correct answer is B. Tone is the writer’s attitude toward the subject and audience; style is the way something is written.
The tone of a text is the attitude that the writer presents toward a topic, and it can be objective, subjective, humorous, ironic, emotional or logical. On the other hand, the style of a text refers to the way it is written, that is to say, the word choices and sentence structures that the author uses to influence in a certain way the reader’s impression about the subject.