Answer:
a) 翌 -> 童 -> 野 -> 預
翌 YOKU - next, following
童 DOU, warabe - child
野 YA, no - field, plain
預 YO, azu(keru), azu(karu) - entrust
b) 岩 -> 硝 -> 削 -> 帰
岩 GAN, iwa - rock
硝 SHOU - saltpeter
削 SAKU, kezu(ru) - whittle down, delete, curtail
帰 KI, kae(ru), kae(su) - return