2729. What characters can be added here so that each character contains a part of the previous character? a) 要 -> _ -> _ -> 坪 b) 架 -> _ -> _ -> 坂

a) 要 -> 如 -> 吐 -> 坪  

要  YOU, i(ru) - essential(s) need

如  JO, NYO - equal, like, as, as if

吐  TOU, ha(ku) - spew, vomit, give vent to

坪  tsubo - unit of area

b) 架 -> 棋 -> 基 -> 坂  

架  KA, ka(keru), ka(karu) - hang, build (a bridge)

棋  KI - go, shogi, Japanese chess

基  KI, moto, motoi - basis, foundation

坂  HAN, saka - slope, hill