Answer:
a) 誓 -> 話 -> 辞 -> 執
誓 SEI, chika(u) - swear, pledge, vow
話 WA, hana(su) - story, talk
辞 JI, ya(meru) - word, resignation
執 SHITSU, SHUU, to(ru) - take, grasp, execute
b) 哲 -> 呈 -> 理 -> 黒
哲 TETSU - wisdom
呈 TEI - offer, present, exhibit
理 RI - reason, logic
黒 KOKU, kuro(i) - black