The number of moles of KMnO4 reduced by one mole of KI in alkaline medium is:

In alkaline medium:

2KMnO₄+H₂O→2KOH+2Mno₂

KI + 3[O ]→ KIO₃

2KMnO₄ + KI + H₂ O→2KOH+2KMnO₂+KIO₃

Hence, the correct option is (b) i.e., 2.