Which of the Following Is NOT One of the Equilibria $\rightleftharpoons$

Multiple Choice

Which of the following is NOT one of the equilibria in the complexation of Ru(II) by ammonia (coordination number = 6) ?

A) Ru²⁺(aq) + NH₃(aq) $\rightleftharpoons$ Ru(NH₃) ²⁺ (aq)
B) Ru²⁺(NH₃) (aq) + NH₃(aq) $\rightleftharpoons$ Ru²⁺(NH₃) ₂ (aq)
C) Ru²⁺(NH₃) ₄ (aq) + NH₃(aq) $\rightleftharpoons$ Ru²⁺(NH₃) ₅ (aq)
D) Ru²⁺(NH₃) ₃ (aq) + NH₃(aq) $\rightleftharpoons$ Ru²⁺(NH₃) ₄ (aq)
E) Ru²⁺(NH₃) ₆ (aq) + NH₃(aq) $\rightleftharpoons$ Ru²⁺(NH₃) ₇ (aq)