Answer:
a) 炎 -> 畑 -> 胃 -> 胞
炎 EN, honou - flame
畑 hatake - cultivated field
胃 I - stomach
胞 HOU - sac, sheath, placenta
b) 早 -> 古 -> 吐 -> 坂
早 SOU, SA, haya(i) , haya(meru) - early, fast, hasten
古 KO, furu(i) - old
吐 TOU, ha(ku) - spew, vomit, give vent to
坂 HAN, saka - slope, hill