The entropy change in adiabatic process is

In the adiabatic process, no heat enters or leaves the system. Therefore, the change in heat equals zero. The change in entropy is the change in heat ($\Delta Q$) of the system per unit rise in temperature. Therefore, for the adiabatic process, the entropy change $\Delta \mathrm{S}$ will always remain constant.

In adiabatic process, $\mathrm{q}=0$

$\therefore \Delta \mathrm{S}=0$

Hence the correct answer is (A) Zero.