Sign up is on a first-come-first-served basis. If you have a conflict on one of these days, please sign up early and choose a time that will not be an issue for you. Because time is limited and it wouldn't be fair to move another student from their time slot to accommodate you without their permission, whenever you sign up for is your official time slot and it will be treated like a test in the sense that you will not be excused if you are unprepared or do not come to class. If you find that you do have a conflict later, you will need to find a classmate with whom to trade presentation spots.