The expression for entropy change, ΔS = nCp.ln ( T_2 T_1 ), is valid for the __________ of a substance.

Answer: Option D

Actually the Entropy of an ideal gas is given by:
$$\Delta S={\int }_{T_i}^{T_f}\frac{C_{p}dT}{T}-nR\ln \left(\frac{P_f}{P_i}\right).$$
$$\Rightarrow$$  it depends upon both temperature and pressure.
Under constant pressure process we can write $$\Delta S=C_p.\ln \left(\frac{T_f}{T_i}\right).$$    The final temperature can be greater or lesser than the initial temperature.