`{:(,"Column-I",,"Column-II"),((a),"Reversible adiabatic compression",(p),"Process in equilibrium"),((b),"Reversible vaporisation of liquid",(q),DeltaS_(system)lt0),((c),2N(g)rarrN_(2)(g),(r),DeltaS_("surrounding")lt0),((d),MgCO_(3)(s)oversetDeltararrMg(s)+CO_(2)(g),(s),DeltaS_("sublimation")=0):}`

Answer

To solve the question, we need to match the items from Column-I with the appropriate items from Column-II based on the principles of thermodynamics, particularly focusing on entropy changes in different processes.

### Step-by-Step Solution:

1. **Reversible Adiabatic Compression (Option a)**:
- In a reversible adiabatic process, there is no heat exchange with the surroundings (Q = 0).
- Since the process is reversible and adiabatic, the change in entropy (ΔS) for the system is zero (ΔS = 0).
- Therefore, **Option a matches with (s) ΔS = 0**.

2. **Reversible Vaporization of Liquid (Option b)**:
- During the vaporization of a liquid, the liquid is converted into gas. This process increases the disorder of the system, leading to an increase in entropy (ΔS > 0).
- Since the process is reversible and occurs at the boiling point, it is also in equilibrium.
- Thus, **Option b matches with (p) Process in equilibrium** and also with (r) ΔS(system) > 0, but since we need to choose one, we will take (p).

3. **2N(g) → N2(g) (Option c)**:
- Here, we have two moles of nitrogen gas (2N) combining to form one mole of nitrogen gas (N2).
- This results in a decrease in the number of gas molecules, which corresponds to a decrease in disorder and thus a decrease in entropy (ΔS < 0).
- Therefore, **Option c matches with (q) ΔS(system) < 0**.

4. **MgCO3(s) ⇌ Mg(s) + CO2(g) (Option d)**:
- In this reaction, solid magnesium carbonate decomposes into solid magnesium and gaseous carbon dioxide.
- The formation of gas from a solid increases the disorder of the system, leading to an increase in entropy (ΔS > 0).
- Therefore, **Option d matches with (r) ΔS(system) > 0**.

### Final Matching:
- a → s (ΔS = 0)
- b → p (Process in equilibrium)
- c → q (ΔS(system) < 0)
- d → r (ΔS(system) > 0)