Read this excerpt from the introduction to Wheels of Change by Sue Macy.

Imagine a population imprisoned by their very clothing; the stiff corsets, heavy skirts, and voluminous petticoats that made it difficult to take a deep breath, let alone exercise. Add to that the laws and social conventions that cemented a man's place as head of the household and holder of the purse strings. How suffocated women must have felt. And how liberated they must have been as they pedaled their wheels toward new horizons.

Why does the author include this excerpt?

to define key terms
to establish credibility
to clearly explain the topic
to offer background information