Correct Answer: LKJM

Solution : Given:
JK_MJ_LM_KL_

To fill in the blanks, divide the series into clusters of 4 letters – JK_M / J_LM / _KL_
Let's check each option –
First option: JKLL; JK J M / J K LM / L KL L (No repeated pattern found.)
Second option: LKKM; JK L M / J K LM / K KL M (No repeated pattern found.)
Third option: LKJM; JK L M / J K LM / J KL M (JKLM is repeated in the series.)
Fourth option: KJLM; JK K M / J J LM / L KL M (No repeated pattern found.)

So, the series becomes→JKLMJKLMJKLM. Hence, the third option is correct.