Correct Answer: IKMG

Solution : Given:
G_KMI_MGK_GIM_IK

To fill the series we have to divide the series – G_KM / I_MG / K_GI / M_IK
Let's check each option –
First option: IIKK; G I KM / I I MG / K K GI / M K IK (No repeated pattern has been found. )
Second option: MGIK; G M KM / I G MG / K I GI / M K IK (No repeated pattern has been found.)
Third option: GGMI; G G KM / I G MG / K M GI / M I IK (No repeated pattern has been found.)
Fourth option: IKMG; G I KM / I K MG / K M GI / M G IK (At each step, the second letter shifts to the first position, the third letter shifts to the second position, the fourth letter shifts to the third position and the first letter shifts to the fourth position.)

So, the series becomes GIKMIKMGKMGIMGIK. Hence, the fourth option is correct.