Seeing how Combat Arms is an online game with no vehicle usage whatsoever, the 75th will have only ONE CMOS section for CA.

Infantry
The backbone of the 75th, 21st Century US Army, and any fighting force. These men make up the bulk of the fighting force.

Officer:
11A: Infantry Officer (This must be earned)

Enlisted:
11B: Infantryman
11X: Infantry Enlistment
11Z: Infantry Senior Sergeant [1SG] This must be earned)

Warrant Officer:
There are none available in Infantry.