Tone is best identified by sorting the passage's actual word choices into categories, then checking which option matches that category, rather than guessing from a general feel.
Sorting the passage's actual words into these categories leaves only one match, the language of grievance and outrage.
So the correct answer is Critical, somber, and resentful, evoking both awareness and outrage.
The word 'technique' in the question means the answer has to name an actual literary device, so testing each option's real definition against how the contrast is used is the most direct method.
Only the allegory option correctly names a sustained, consistent stand-in for a real social and economic system rather than a single figure of speech or a biological description.
So the correct answer is Allegory of class exploitation.
This is a precise-definition question, so each option needs to be checked word by word against the standard meaning of 'knacker,' not just approved or rejected in a general sense.
Matching the full definition, disposal work plus animals unfit for human food, against the passage's own detail about Boxer confirms the third option as the exact fit.
So the correct answer is A person whose business is disposal of dead or unwanted animals especially those whose flesh is not fit for human consumption.
The question specifically asks about the effect of repeating these harsh images, so the answer should explain what repetition itself accomplishes, not just what the images mean once.
Piling up specific violent examples one after another is a deliberate rhetorical build-up meant to provoke anger at how the animals are treated, not to inform, reassure, or normalise it.
So the correct answer is Evoke emotional outrage and highlight the brutality of exploitation.