1039. What character can be added to both of these characters to give other characters? 北_ -> _却

Answer:

北  HOKU, kita - north

却  KYAKU - pull back, withdraw

Add 月:北+月 月+却 

月  GETSU, GATSU, tsuki - moon, month

背  HAI, se, somu(ku), somu(keru) - back, height, act contrary to, avert

脚  KYAKU, KYA, ashi - leg