Answer:
a) 架 -> 柱 -> 青 -> 肪
架 KA, ka(keru), ka(karu) - hang, build (a bridge)
柱 CHUU, hashira - pillar, column, pole
青 SEI, SHOU, ao(i) - blue
肪 BOU - animal fat
b) 弦 -> 畜 -> 累 -> 絶
弦 GEN, tsuru - string, bowstring
畜 CHIKU - animal raising, domestic animal
累 RUI - involvement, trouble, accumulation
絶 ZETSU, ta(eru), ta(tsu), ta(yasu) - die out, end, cut off, interrupt, kill off