2707. What characters can be added here so that each character contains a part of the previous character? a) 針 -> _ -> _ -> 販 b) 炎 -> _ -> _ -> 結

a) 針 -> 古 -> 員 -> 販  

針  SHIN, hari - needle

古  KO, furu(i) - old

員  IN - member

販  HAN - sell

b) 炎 -> 畑 -> 累 -> 結  

炎  EN, honou - flame

畑  hatake - cultivated field

累  RUI - involvement, trouble, accumulation

結  KETSU, musu(bu), yu(u) - tie up, bind