Identfy the palnts with same type of modified underground stems

(I) Amorphophallus, Lilium
(II) Colocasia, Colchicum
(III) Curcuma, Gloriosa
(IV) Potato, Banana
(a) (I), (II)
(b) (I), (IV)
(c) (II), (IV)
(d) (II), (III)