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

Answer:

士  SHI - samurai, man, scholar

及   KYUU, oyo(bu), oyo(bosu) - reach, amount to, match, equal

Add 口:士+口 口+及 

口  KOU, kuchi - mouth

吉  KICHI, KITSU, yoshi - good luck

吸  KYUU, su(u) - suck, inhale, smoke