In which of the following,the tendency towards the formation of coloured ions is maximum?

Given below are two statements: one is labelled as Assertion $(A)$ and the other is labelled as Reason $(R)$.
Assertion $(A):$ $Cu^{2+}$ in water is more stable than $Cu^{+}$.
Reason $(R):$ Enthalpy of hydration for $Cu^{2+}$ is much less than that of $Cu^{+}$.
In the light of the above statements,choose the correct answer from the options given below:

Which of the following elements can form complex ions?

$Cr^{2+}$ has a magnetic moment same as that of

Which of the following ions is coloured?

The aqueous solutions of the following salts will be coloured in the case of: