During the Physical changes
I believe the correct answer is C, but I'm 100% on this. Hope this helped though!
-TTL
To find the net ionic equation we must first write the balanced equation for the reaction. We must bear in mind that the reagents Ca(NO3)2 and Na2S are in the aqueous state and as product we will have CaS in the solid state, since it is not soluble in water and NaNO3 in the aqueous state.
The balanced equation of the reaction will be:

Ca(NO3)2(aq) + → Ca(aq) + 2Na(s)NO3Now, c(aq)ompounds in the aqueous state can be written in their ionic form, so the reaction will transform into:Na2S +

So, the answer will be option A
The water dissolves the salt because the water molecules are able to interact with the salt-forming particles, called ions. When the water Interacts with the trainers of the salt ions, the solid salt crystal structure Suffers breakdown, until the trainers of the salt ions are completely surrounded by water molecules. At this time the salt is fully dissolved by water.
hope this helps!