Complete the series:
EPFS, GPHS, IPJS, _________, MPNS

We can see that the 2nd and the 4th letter of the given series is P and S.
The 1st word and the 3rd word is every alternative word.
i.e. E in 1st word is followed by G in 2nd word and G is followed by I in the 3rd word and thus, K should be there in the 4th word.
The 1st and the 2nd letter of any word are consequtive letters and thus, 3rd word should be L.
Hence, the correct word = KPLS.
Hence, option D is the correct answer.