Pressure

Step 1: Understand the Freundlich adsorption isotherm.
The Freundlich adsorption isotherm is given by: where is the amount of adsorbate per unit mass of adsorbent, is the pressure, and and are constants.
The exponent reflects the degree of adsorption.
Step 2: Behavior at different pressure ranges.
At low pressures, the adsorption is approximately proportional to the pressure, .
As pressure increases, the adsorption follows , where is greater than 1.
At very high pressures, the system may reach saturation, and the adsorption could approach a constant value .
Step 3: Conclusion.
All these relations are correct for different ranges of pressure, hence option (d) is correct.