Based on the provided options, the repetition of "if" in the poem suggests that the speaker's advice is not necessary for his son to become a man. This aligns with option D. The poem presents a series of hypothetical situations using "if," outlining various challenges and qualities the son should possess. By using "if" repeatedly, the poem sets up conditional statements that imply the speaker's acknowledgment of the difficulties and uncertainties his son may encounter. It emphasizes the importance of maintaining composure, integrity, and self-belief in the face of adversity. The repetition of "if" implies that these qualities are not yet fully present in the son but should be strived for in order to become a proper adult.