A: All armoured vehicles. Not just tanks. Can include Bionix,
M113 Ultra, maybe even the V200. Now that SAF has the Primus, I'm
guessing Primus can also be considered "A" vehicle.
B: All unarmoured wheeled vehicles like 5 tonner, 7 tonner, Unimog,
recce jeep, command jeep, landrover, GP car, recovery truck, etc.
Emphasis on unarmoured 'cos the V200 is wheeled but is armoured so
it wouldn't be considered "B".
C: I'm not too sure about this category but I believe it includes
stuff like excavators, bulldozer, chain saw, trailers, tugboats,
etc. Am quite sure about the last 4 I listed 'cos I was a "B" mech
& I know a few "C" mech.
I believe bridging engineer vehicles e.g. Candace, almond, comet,
etc MAY also fall under "C".