584. What character can be added to both of these characters to give other characters? 日_ -> _干

Answer:

日  NICHI, JITSU, hi, ka - sun, day

干  KAN, hi(ru), ho(su) - get dry, dry, drink up

Add 月: 日+月 月+干 

月  GETSU, GATSU, tsuki - moon, month

明  MEI, MYOU, aka(rui), a(keru) - bright

肝  KAN, kimo - liver, heart, spirit