Question

As carbon dioxide sublimates from a solid into a gas, what is happening to the pressure if the temperature is remaining constant?

Answer 1

pressure is lowered cause by lowering pressure you move equilibrium towards gaseous state (le chaterlier principle)

Answer 2

I would say pressure increases until equilibrium vapour pressure at given temperature is reached.

Answer 3

it can only sublimate if pressure is low enough for it to sublimate, if pressure is higher then it is necessary for pressure to be lowered...
but yeah i got your point if pressure was stable and CO2 sublimates pressure would rise until equilibrium...