Cannot unlock the MTAR-21 (Multi talent assignment)

I looked at your battlelog profile here: http://battlelog.battlefield.com/bf4/soldier/Oxive/assignments/903415418/pc/#xp1as04

You first need to earn 3 anti-vehicle ribbons after downloading the China Rising expansion, and then you need to kill an aircraft with a stinger or IGLA anit-aircraft rocket. After those requirements are met the MP7 will unlock for you.