An example of antithesis in the given sentences is the contrasting relationship between the ideas in sentence A and sentence C. In sentence A, the idea is that Emma only makes cookies when Evan is not present, while in sentence C, the idea is that Evan loves eating the cookies whenever Emma makes them. These ideas are in contrast to each other, as they present opposing perspectives on the same action (Emma making cookies). This creates a sense of balance and contrast between the two ideas, which is a common characteristic of antithesis.