Answer:
a) 案 -> 棋 -> 期 -> 脂
案 AN - plan, proposal
棋 KI - go, shogi, Japanese chess
期 KI, GO - time, period, term
脂 SHI, abura - fat
b) 雷 -> 男 -> 加 -> 嘱
雷 RAI, kaminari - thunder
男 DAN, NAN, otoko - male, man
加 KA, kuwa(eru), kuwa(waru) - add, append, join, take part
嘱 SHOKU - request, entrust, commission