ANS:A - are different

Equilibrium-moisture curves of different solids are different. The equilibrium-moisture curve represents the relationship between the moisture content of a solid and the relative humidity of the surrounding air at equilibrium. This relationship depends on various factors such as the specific properties of the solid material (e.g., porosity, surface area, hygroscopicity), as well as the temperature and pressure conditions. Different solids have different physical and chemical properties that influence their ability to absorb and retain moisture from the surrounding environment. Therefore, the equilibrium-moisture curves of different solids will vary depending on these factors.