Final answer:
Option c effectively uses figurative language resembling a distant sign to create a sad mood by evoking a sense of fading memory.
Step-by-step explanation:
The best way to revise sentence 2 using figurative language to create a sad mood in the narrative is option c: "It all seems so long ago now, like a sign standing on the distant horizon." This option uses the metaphor of a distant sign to evoke a sense of remoteness and fading memory, which contributes to a sad mood. It suggests that the memories are as difficult to grasp as a barely visible sign far away. This contrasts with options a, b, and d, which do not employ figurative language as effectively to create a melancholic atmosphere.