Maybe this will help, although as Flamgat says, saturation is a rather complex subject so what follows is not the full story.
Water Phase Diagram
ISA at sea level is 288K and around 1015 HPa (~10 to the power 5 Pa). Temperature changes in the troposhere are of the order of 200-320K, and pressure from 200-1050 HPa. Although the phase diagram indicates sudden state transitions, in the atmosphere they are actually equilibria - vapour in equilibrium with solid and liquid. This is because the atmosphere is a mixture of compounds as opposed to the pure water situation shown in the diagram.
It's clear from the diagram that (a) is right since the transition is right to left with a slight downward slope to the left. The equilibrium is therefore pushed in favour of liquid (ie condensation/saturation)
If you're restricted to vertical movements (constant temperature), only rises in pressure will cause saturation (transition to liquid state) so (d) might be technically correct.
As several posts have pointed out temperature effects in the atmosphere dominate (the pressure scale is a log one on the graph) so (d) is unlikely to prevail in an atmospheric situation. However, since the question itself has posited the situation in (d) - however unlikely - I suppose you have to accept that it's a true answer.
It could certainly be true in the lab, so if you take the lawyer's approach you could appeal it since parcel size is not defined and hyperbaric chambers are not excluded as 'areas' ! Might be easier to give them the answer they want though.