2088. What characters can be added here so that each character contains a part of the previous character? a) 架 -> _ -> _ -> 績 b) 菓 -> _ -> _ -> 腰

a) 架 -> 柱 -> 素 -> 績  

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

柱  CHUU, hashira - pillar, column, pole

素  SO, SU - element, naked, simple

績  SEKI - achievements, spinning

b) 菓 -> 棋 -> 期 -> 腰  

菓  KA - cake, fruit

棋  KI - go, shogi, Japanese chess

期  KI, GO - time, period, term

腰  YOU, koshi - pelvis, loins, hips, back