He could have made backups of both discs when he bought the game, and stored them in a safe place in case the disc got lost or broken.
He can copy the working disc and use it to play multiplayer games. Each disc only has half of the single-player game, but both discs are identical for multiplayer games. If he and his roommate both have a copy of the same disc, they can still play against each other.
Thanks everybody for the information it seems that people are telling me two things but I can better make a decision with the info. I won’t be able to check this fourm untill jan 4th but if anybody has anything else to add please do I always check my threads.