Correct answer: C) 1850s
Details:
Harriet Tubman was an escaped slave. who had been held in slavery in Maryland. She escaped to Philadelphia in 1849 ... but then went back to rescue her family and help them to freedom. Then she helped extended family members, and eventually was helping many, many slaves to freedom on what became known as the "Underground Railroad" -- a secret network of routes from one safe house to another that aided slaves in their escape. During the 1850s, Tubman directly helped dozens of slaves escape to the North, and provided instructions for escape to dozens more beyond those.