Select the combination of letters that when filled in the blanks in the same sequence will make the series logically complete.

_ B F K G _ H M I F _ O K H L _ M J N _

Given: _ B F K G _ H M I F _ O K H L _ M J N _

Now, we check each options.

Option (a): EFJRS (Not Follow)​

E B / F K / G F / H M / I F / J O / K H / L R / M J / N S

Option (b): CDKQT (Not Follow)​

C B / F K / G D / H M / I F / K O / K H / L Q / M J / N T

Option (c): EDJQS (Follow)​

E B / F K / G D / H M / I F / J O / K H / L Q / M J / N S

Option (d): CFKRT (Not Follow)

C B / F K / G F / H M / I F / K O / K H / L R / M J / N T

So, the following pattern is: - 3 and + 5 alternately

Thus, correct option is (c).