Ans :JKJ alphabets in ascending order 1st and 3rd letter same and middle is one letter ahead, alternative series.
JKJ 1st letter and 3rd letter are same but the middle letter are the next letter of 1st and 3rd letter
To solve this question, make first and third character same and second character is next to next of I Ans :- JKJ
SEQUENCE: BCB DED FGF HIH JKJ The answer is JKJ