Answer:
a) 雷 -> 累 -> 紛 -> 盆
雷 RAI, kaminari - thunder
累 RUI - involvement, trouble, accumulation
紛 FUN, magi(reru), magi(rawashii) - be mistaken for, confusing
盆 BON - festival of the dead, tray
b) 劣 -> 加 -> 員 -> 贈
劣 RETSU, oto(ru) - be inferior
加 KA, kuwa(eru), kuwa(waru) - add, append, join, take part
員 IN - member
贈 ZOU, SOU, oku(ru) - give, present, bestow