When KMnO₄ acts as an oxidising agent and ultimately forms [MnO₄]⁻¹, MnO₂, Mn₂O₃, Mn²⁺ then the number of electrons transferred in each case respectively is:

(a) 4, 3, 1, 5
(b) 1, 5, 3, 7
(c) 1, 3, 4, 5
(d) 3, 5, 7, 1.