Select the combination of letters that when sequentially placed in the blanks of the given letter series will complete the series.

e_geef_gg_ee_f_ggg

By Trial and Error method,

Option A

egg | eeffgg | eeefffggg

The above letters do not form a series. Hence option A is incorrect.

Option B

efg | eeffgg | feefffggg

The above letters do not form a series. Hence option B is incorrect.

Option C

efg | eefggg | feegfgggg

The above letters do not form a series. Hence option C is incorrect.

Option D

efg | eeffgg | eeefffggg

The above letters form a series.

Hence, the correct answer is Option D