Honestly if you are actually interested in a game you shouldn't watch the trailer and then blindly buy the game. But then again most people are mindless consumers.
@xboxfanonly halopedian has a ton of info on the subject. Carter is 32, he was one of the first Spartan-IIIs which was started in 2531 making him 11 when he was drafted. Noble Team was under the command of the UNSC Army while the Spartan program is part of the UNSC Navy so it's entirely plausible that Noble was marked MIA to the Navy but secretly working for the Army. Again it's a pretty massive plot hole that 343 has yet to explain but Noble was a Spec Ops team so it's likely that their existence was on a 'need to know' basis.
@xboxfanonly No it's stated multiple times that the rest of Noble team are Spartan-III's, it's a plot hole they have yet to fill. The only Spartan I (also known as project orion) that you see in the games is Sgt. Johnson.
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