For a sample of perfect gas when its pressure is changed isothermally from pᵢ to p, the entropy change is given by:

A. ΔS = nR ln(pᵢ/p)
B. ΔS = nRT ln(p/pᵢ)
C. ΔS = RT ln(pᵢ/p)
D. ΔS = nR ln(p/pᵢ)