Answer:
a) 篤 -> 駐 -> 責 -> 販
篤 TOKU - serious, cordial
駐 CHUU - stop, reside
責 SEKI, se(meru) - condemn, censure, torture
販 HAN - sell
b) 架 -> 棋 -> 碁 -> 碑
架 KA, ka(keru), ka(karu) - hang, build (a bridge)
棋 KI - go, shogi, Japanese chess
碁 GO - go (board game)
碑 HI - tombstone, monument