Answer:
a) 社 -> 埋 -> 野 -> 預
社 SHA, yashiro - shrine, company
埋 MAI, u(maru), u(meru), u(moreru) - bury, be buried, filled up
野 YA, no - field, plain
預 YO, azu(keru), azu(karu) - entrust
b) 祖 -> 助 -> 加 -> 味
祖 SO - ancestor
助 JO , tasu(keru), suke - help, rescue, assistance
加 KA, kuwa(eru), kuwa(waru) - add, append, join, take part
味 MI, aji , aji(wau) - taste