You Are Having Lunch with Your Friends, Oliver, Julia, and Richard

You are having lunch with your friends, Oliver, Julia, and Richard, and you are discussing the link between homework and exam grades. Oliver says, "I know that doing homework improves exam grades because I always do my homework and I have a 4.0." Julia says, "I know that doing homework improves exam grades because a blog I read on an education website says so." Richard says, "I know that doing homework improves exam grades because that makes sense. Teachers would not assign it if it did not." Provide a response to each friend for why his or her reasoning is unsound.