Considering entropy (S) as a thermodynamic parameter, the criterion for the spontaneity of any process is:

• Correct answer
  A

  $\Delta \mathrm{S}_{\text {system }}+\Delta \mathrm{S}_{\text {surrounding }}>0$
• B

  $\Delta \mathrm{S}_{\text {system }}-\Delta \mathrm{S}_{\text {surrounding }}>0$
• C

  $\Delta \mathrm{S}_{\text {System }}>0$ only
• D

  $\Delta \mathrm{S}_{\text {Surroundings }}>$ only

Solution

According to Second Law of Thermodynamics, for a spontaneous process, total change in entropy (system + surrounding) should be positive.
Related Theory (Ref. to Fig. 28.1)
For the latter two cases, the temperature at which the spontaneity changes will be determined by the relative magnitudes of $\triangle S$ and $\Delta H$.

Hence, the correct answer is option: 'A'.