Which of the following complexes formed by Cu²⁺ ions is most stable?

_{K is called the equilibrium constant( or binding constant) and tells us how strongly the ligands bind to the metal centre. So, the higher the value of K, the greater the stability of the complex formed.}

K=

Greater the value of K, the equilibrium is favoured more towards the side of the formation of complex, which is possible only if it is very stable.

Thus, Option B is the correct answer.