Zero fuel mass is
Basic empty Mass + variable Load + Traffic Load.
In other words
Weight of the plane
Crew, Crew Baggage and special Equipment
Passengers
Freight
In this case I would have to say the answer was D . If the answer looked for the Maxiumum Zero Fuel Mass then A would be correct but that would mean that maximum weight that could be allow with out any fuel loaded where as this question is just asking for the ZFM Ie the weight of the plane without any fuel, which has to be the total mass of the plane at takeoff minus the take off fuel mass. Hope this helps