halo 3 graduate achievement not unlocked?

[Rumon]

im a captain and got all other of the ranking achievements like spartan officer and spartan insignia.i got the achievements for those ones but didnt get the graduate achievement. if you know what to do just post your answer, if you say e-mail bungie can you say what bungies email adress is? thanks btw my GT eadlyAssasin95

 

[Devon]

Check out this website for your answer...........


www.gamespot.com

Then type in the game in the top

hope this helps!