(just want to check my answer)

what fact is the most important indicator that the following reaction will take place?

Ni(No3)2)aq) + K2S(aq) NiS(s) + 2KNO3(aq)

A) The reaction is a double displacement *my answer*
B) A precipitate is formed.
C) The reactants are ionic compounds.
D) The products are ionic compounds.