2426. What character can be added to both of these characters to give other characters? 矛_ -> _古

矛  MU, hoko - halberd, spear

古  KO, furu(i) - old

Add 木:矛+木 木+古  

木  MOKU, BOKU, ki - tree

柔  JUU, NYUU, yawa(rakai) - soft

枯  KO, ka(reru), ka(rasu) - wither