1241. What character can be added to both of these characters to give other characters? 士_ -> _欠

Answer:

士  SHI - samurai, man, scholar

欠  KETSU, ka(ku), ka(keru) - lack

Add 口:士+口 口+欠 

口  KOU, kuchi - mouth

吉  KICHI, KITSU, yoshi - good luck

吹  SUI, fu(ku) - blow