the reaction KI + I₂ -> KI₃

a. oxidation

b.reduction

c.complex formation

d.all

KI when react with Iodine forms a complex KI₃. In this reaction, I^- form KI get oxidized and I₂ gets reduced. Thus in this reaction all the three oxidation, reduction and complex formation occurs. So, the correct answer is option (d). All.