Answer: The right answer is the B) Speaking in a way that uses irony to mock or make fun of someone or something.
Explanation: Just to elaborate a bit on the answer, it can be added that sarcasm, from the Latin sarcasmus and the Greek sarkasmos ("a hurtful remark"), is a very cruel and biting form of irony or mockery that aims at offending someone or something. Sarcasm is also used to convey contempt. A Farewell to Arms, like other novels by Hemingway, speaks of loss, death, pain, dispair, disillusionment, violence, destruction and war. The use of sarcasm, or sarcastic remarks, in his characters seems, therefore, justified, or it can be understood as a mechanism that helps them to cope with the challenging and often devastating life events that they experience.