ANS:D - all (a), (b) and (c).

Nature of the Moisture:

1. • The nature of the moisture refers to its chemical composition and physical properties. Different substances may have different vapor pressures at the same temperature due to variations in molecular size, polarity, and interactions with the solid material.
   • For example, water vaporizes more readily than some other liquids at the same temperature due to its relatively low molecular weight and strong hydrogen bonding, which results in higher vapor pressure.
   • The chemical composition of the moisture can also affect its vapor pressure. For instance, volatile organic compounds (VOCs) may have higher vapor pressures compared to water under certain conditions.
2. Temperature:
   • Temperature plays a crucial role in determining the vapor pressure of moisture in a wet solid. As temperature increases, the kinetic energy of the molecules also increases, leading to more molecules escaping from the solid surface into the vapor phase.
   • The relationship between temperature and vapor pressure is described by vapor pressure curves specific to each substance. Generally, as temperature increases, vapor pressure also increases, following principles such as the Clausius-Clapeyron equation.
3. Nature of the Solid:
   • The nature of the solid indirectly influences the vapor pressure of moisture through factors such as surface area, porosity, and adsorption capacity.
   • A solid with a larger surface area provides more sites for moisture molecules to evaporate into the vapor phase, potentially increasing vapor pressure.
   • Porous solids may have higher vapor pressures because they can trap moisture within their structure, increasing the effective surface area for vaporization.
   • The adsorption capacity of the solid, or its ability to hold moisture on its surface, can also affect vapor pressure by influencing the equilibrium between moisture in the solid and vapor phases.

In summary, the vapor pressure exerted by the moisture in a wet solid depends on multiple factors, including the nature of the moisture, temperature, and the nature of the solid. Each of these factors contributes to the overall vapor pressure behavior of the system.