This week's book giveaway is in the OCPJP forum. We're giving away four copies of OCA/OCP Java SE 7 Programmer I & II Study Guide and have Kathy Sierra & Bert Bates on-line! See this thread for details.
Yeah... they allow you to mark the answers that you are not sure of and it should remind you to look over the "marked" answers at the end. You can look over and change any other unmarked answer too, it is just easier to mark them as you go. Hope that helps.