Your choices were the following:

• (a) Bark like a dog.
• (b) Say, "Actually I find dogs quite attractive."
• (c) Say, "It's because I like to beat my face with large sticks."
• (d) Say, "So's your mother."

All are good choices, because they are unexpected and cause pain. Remember, however, that pain is only funny when it happens to someone else, so (d), which deflects the insult rather than amplifying it, is the correct choice.