879. What character can be added to both of these characters to give other characters? 其_ -> _曽

Answer:

其  shi, so - that

曽  SOU, katsute - overlap

Add 土:其+土 土+曽

土  DO, tsuchi - earth, soil

基  KI, moto, motoi - basis, foundation

増  ZOU, ma(su), fu(eru), fu(yasu) - increase, rise, raise