Answer: C. Surgery.
Step-by-step explanation: The tone of a text or a story is the author's attitude towards the audience, the theme or even the characters of a story. There are many different kinds of tone, positive, negative, happy, sad, angry, etc. In the given excerpt the word that creates a negative tone toward the tractor is "surgery" because it gives the idea of the tractor cutting the earth in a precise but heartless way, like doing a surgery.