Final answer:
In a piston–cylinder assembly with a poorly conducting piston and no friction, the internal gas pressure must remain constant and positive to balance the weight of the piston and atmospheric pressure as the piston moves, making the correct answer Option C: constant and positive.
Step-by-step explanation:
The student question is asking to determine the nature of the gas pressure inside a piston–cylinder assembly as a response to a given process. Looking at the system, a force balance on the piston must account for the weight of the piston and the atmospheric pressure, in addition to the internal gas pressure. The weight of the piston and the atmospheric pressure are constants, and if we assume that there is no change in temperature and no heat loss (poor thermal conductors), according to the descriptions of processes in a piston-cylinder system, the internal gas pressure must remain constant to balance the forces as the piston moves up.
Therefore, we can infer that the gas pressure must remain constant to counterbalance the weight of the piston and the atmospheric pressure. This means the answer to the question is Option C: constant and positive.