2072. What characters can be added here so that each character contains a part of the previous character? a) 弦 -> _ -> _ -> 絡 b) 柔 -> _ -> _ -> 胞

a) 弦 -> 畜 -> 累 -> 絡  

弦  GEN, tsuru - string, bowstring

畜  CHIKU - animal raising, domestic animal

累  RUI - involvement, trouble, accumulation

絡  RAKU, kara(mu), kara(maru) - be entangled

b) 柔 -> 棋 -> 期 -> 胞  

柔  JUU, NYUU, yawa(rakai) - soft

棋  KI - go, shogi, Japanese chess

期  KI, GO - time, period, term

胞  HOU - sac, sheath, placenta