2531. What characters can be added here so that each character contains a part of the previous character?


a) 動 -> 加 -> 吟 -> 含  

動  DOU , ugo(ku) - move

加  KA, kuwa(eru), kuwa(waru) - add, append, join, take part

吟  GIN - sing, chant, recite

含  GAN, fuku(mu), fuku(meru) - hold, include, contain

b) 弦 -> 畜 -> 胃 -> 肝  

弦  GEN, tsuru - string, bowstring

畜  CHIKU - animal raising, domestic animal

胃  I - stomach

肝  KAN, kimo - liver, heart, spirit