Which one set of letters when sequentially placed at the gaps in the given letter series shall complete it?
g _ _ g _ _ g h _ g _ i

Given: g _ _ g _ _ g h _ g _ i

Now, we check each options.

Option (a): h i h i i h

g hi / g h i / g h i / g h i

Option (b): h h i i h h

g h h / g i i / g h h / g h i

Option (c): j k l j k l

g j k / g l j / g h k / g l i

Option (d): h i j k l i

g h i / g j k / g h l / g i i

So, the following pattern is: g h i

Thus, correct option is (a).