Final answer:
Nick's remark about being thirty symbolizes a reflective point in his life, acknowledging both achievements and the inevitable process of aging.
Step-by-step explanation:
The comment Nick makes about being thirty suggests a sense of introspection and realization of aging. The use of age in literature is a common theme to depict personal growth, the passage of time, or coming to terms with one's own mortality. In the various excerpts provided, age is used to convey the weight of personal experience, retrospection, or as a milestone in character development.
For example, in F. Scott Fitzgerald's "The Rich Boy," age is associated with wealth and status, reflecting societal expectations and personal ambitions. Meanwhile, the reference to "threescore years and ten" in the poem alludes to the biblical lifespan of a human, summing up a life span's benchmark.