a) 炎 -> 畑 -> 胃 -> 肥
炎 EN, honou - flame
畑 hatake - cultivated field
胃 I - stomach
肥 HI, koe, ko(yashi), ko(yasu) - manure, fertilizer, grow fat
b) 弦 -> 畜 -> 里 -> 坂
弦 GEN, tsuru - string, bowstring
畜 CHIKU - animal raising, domestic animal
里 RI, sato - village
坂 HAN, saka - slope, hill