Answer:
a) 炎 -> 畑 -> 胃 -> 脚
炎 EN, honou - flame
畑 hatake - cultivated field
胃 I - stomach
脚 KYAKU, KYA, ashi - leg
b) 切 -> 召 -> 吐 -> 堤
切 SETSU, ki(ru), ki(reru) - cut
召 SHOU, me(su) - summon, wear, take
吐 TOU, ha(ku) - spew, vomit, give vent to
堤 TEI, tsutsumi - bank, embankment, dike