Letter series type of questions usually consists of a series of small letters which follow a certain pattern. However, some letters are missing from the series. These missing letters are then given in a proper sequence as one of the alternatives. The candidate is requitred to choose this alternative as the answer.
gfe _ ig _ eii _ fei _ gf _ ii
The series is gfeii / gfeii / gfeii / gfeii.
Thus, the pattern gfeii is repeated.