Which element is not present in Nessler's reagent?

Given below are two statements : one is labelled as Assertion (A) and the other is labelled as Reason (R).

Assertion (A) : $$\mathrm{Cu^{2+}}$$ in water is more stable than $$\mathrm{Cu^{+}}$$.

Reason (R) : Enthalpy of hydration for $$\mathrm{Cu^{2+}}$$ is much less than that of $$\mathrm{Cu^{+}}$$.

In the light of the above statements, choose the correct answer from the options given below :

Given below are two statements:

Statement I: Chlorine can easily combine with oxygen to form oxides; and the product has a tendency to explode.

Statement II: Chemical reactivity of an element can be determined by its reaction with oxygen and halogens.

In the light of the above statements, choose the correct answer from the options given below