2283. What characters can be added here so that each character contains a part of the previous character? a) 弦 -> _ -> _ -> 綱 b) 案 -> _ -> _ -> 坪

a) 弦 -> 畜 -> 累 -> 綱  

弦  GEN, tsuru - string, bowstring

畜  CHIKU - animal raising, domestic animal

累  RUI - involvement, trouble, accumulation

綱  KOU, tsuna - rope

b) 案 -> 棋 -> 基 -> 坪  

案  AN - plan, proposal

棋  KI - go, shogi, Japanese chess

基  KI, moto, motoi - basis, foundation

坪  tsubo - unit of area