2164. What character can be added to both of these characters to give other characters? 安_ -> _反

安  AN, yasu(i) - peace, cheap

反  HAN, HON, tane, so(ru) - anti-, bend back

Add 木:安+木 木+反  

木  MOKU, BOKU, ki - tree

案  AN - plan, proposal

板  HAN, BAN, ita - board