The above mentioned sentence would have Option A, “writer” as the answer.
In the sentence, there are several nouns which are given: complaint, board, the air-hostess and the writer. The air-hostess is specifically a feminine noun and cannot be used for males and the rest, i.e., option B and C, complaint and board are both neutral nouns, which do not carry the sense of a specific gender. Whereas Option A, writer, can be used for both the genders, irrespective of the both.
Thus, Option A, is the correct answer.