$K_4[Fe(CN)_6]$ can be used to detect one or more out of $Fe^{2+}, Fe^{3+}, Zn^{2+}, Cu^{2+}, Cd^{2+}$

Question

(a) $Fe^{2+}, Fe^{3+}$
(b) $Fe^{3+}, Zn^{2+}, Cu^{2+}$
(c) All but $Fe^{3+}$
(d) All but $Fe^{2+}$