For the following Assertion and Reason, the correct option is
Assertion (A) : When $\require{mhchem}\ce{Cu (II)}$ and sulphide ions are mixed, they react together extremely quickly to give a solid.
Reason (R) : The equilibrium constant of $\require{mhchem}\ce{Cu^2+ (aq) + S^2- (aq)<=>CuS(s)}$ is high because the solubility product is low.
(1) (A) is false and (R) is true.
(2) Both (A) and (R) are false.
(3) Both (A) and (R) are true but (R) is not the explanation for (A).
(4) Both (A) and (R) are true and (R) is the explanation for (A).