The most appropriate statement that analyzes how the poem reflects themes and issues of its time period is:
The poem’s themes of triumph and tragedy reflect the benefits and challenges of the development of big cities in the United States.
This choice captures the dual nature of the poem, highlighting both the pride and vibrancy of Chicago as a center of industrialization and the darker aspects associated with urban life, such as violence and poverty. Sandburg celebrates the city's strength and resilience while also acknowledging its flaws, embodying the complexities of urbanization during that era.