Solution:We put all the option in blank area and check who create particular pattern
F _ HTFKO _ _ RVTFY _ T F _ JT
UJHNH โ F U H T / F K O J / H R V T / F Y N T / F H J T
DHJNF โ F D H T / F K O H / J R V T / F Y N T / F F J T
JFJMH โ F J H T / F K O Fย / J R V T / F Y M T / F H J T
But,
DTFCF โ F D H T / F K O T / F R V T / F Y C T / F F J T
The 1st and 4th letters are not changing and the 2nd and 3rd letters are increasing by 7.
Hence, "DTFCF" is the correct answer.