The best response to how the use of rhetorical questions in this excerpt advances Clarence Darrow's purpose of persuading the judge to give a lighter sentence is:
b The rhetorical questions imply that a harsher sentence would only serve to make people crueler.
This response accurately captures the essence of Darrow's argument, as he uses rhetorical questions to evoke thought about the consequences of cruelty and the cycle of hatred and violence that can result from a harsh punishment.