The Underground Railroad wasn't underground and it wasn't a railroad. But it was real just the same. And it was one of the brightest chapters in American history.        The Underground Railroad was a secret network of people who helped slaves flee to freedom before the Civil War. The slaves were black people from families who had been brought from Africa in chains. They were owned by their white masters and forced to work without pay.        The first slaves arrived inprefix = st1 /Jamestown,Virginiain 1619. Two hundred years later, there were nearly four million slaves in theUnited States. Most worked in large plantations in the South. By then, slavery had been outlawed in most northern states.        Many slaves were treated cruelly. Some were not. All could be bought and sold. Some slaves bought their own freedom by earning money during time off from work at the plantation. There were free black people in both the North and South during slavery days.        Thousands of slaves ran away each year. Some fled to get away from harsh masters. Others wanted to enjoy liberty. The Underground Railroad was started to help them.        The "station" of the Underground Railroad were homes, shops, and churches where runaway slaves were hidden and fed. The "agents" or "stationmasters" were people --- both black and white --- who hated slavery. They wanted to help slaves get free.       "Conductors" on the Underground Railroad led or transported fugitives from station to station on their way to free states. They had to watch for slave catchers, who were paid to capture runaways and return them. Some conductors guided slaves all the way to Canada.        The most famous conductor was Harriet Tubman. She was a strong, determined woman. Before she became a conductor, Mrs. Tubman had been a passenger on a dangerous journey on the Underground Railroad.        She lived as a slave on the plantation inMaryland. One day in 1849, Mrs. Tubman heard that she was going to be sold. She decided to escape instead.        Harriet Tubman walked away from the plantation that night. She followed the North Star toward the free state ofPennsylvania90 miles away. Sometimes she hiked all night, from station to station on the Underground Railroad. Once she was hidden under blankets and vegetables in a farm wagon, and she rode through the night. Another time she was carried in a rowboat for miles.        She got toPennsylvaniaone morning just at sunrise. This story is mainly about   _  .
Harriet Tubman, the most famous conductor on the Underground Railroad America's Underground Railroad System how people in the United Statesused a secret network to help free slaves why nearly 4,000,000 slaves arrived in the United States
Question: The Underground Railroad wasn't underground and it wasn't a railroad. But it was real just the same. And it was one of the brightest chapters in American history.        The Underground Railroad was a secret network of people who helped slaves flee to freedom before the Civil War. The slaves were black people from families who had been brought from Africa in chains. They were owned by their white masters and forced to work without pay.        The first slaves arrived inprefix = st1 /Jamestown,Virginiain 1619. Two hundred years later, there were nearly four million slaves in theUnited States. Most worked in large plantations in the South. By then, slavery had been outlawed in most northern states.        Many slaves were treated cruelly. Some were not. All could be bought and sold. Some slaves bought their own freedom by earning money during time off from work at the plantation. There were free black people in both the North and South during slavery days.        Thousands of slaves ran away each year. Some fled to get away from harsh masters. Others wanted to enjoy liberty. The Underground Railroad was started to help them.        The "station" of the Underground Railroad were homes, shops, and churches where runaway slaves were hidden and fed. The "agents" or "stationmasters" were people --- both black and white --- who hated slavery. They wanted to help slaves get free.       "Conductors" on the Underground Railroad led or transported fugitives from station to station on their way to free states. They had to watch for slave catchers, who were paid to capture runaways and return them. Some conductors guided slaves all the way to Canada.        The most famous conductor was Harriet Tubman. She was a strong, determined woman. Before she became a conductor, Mrs. Tubman had been a passenger on a dangerous journey on the Underground Railroad.        She lived as a slave on the plantation inMaryland. One day in 1849, Mrs. Tubman heard that she was going to be sold. She decided to escape instead.        Harriet Tubman walked away from the plantation that night. She followed the North Star toward the free state ofPennsylvania90 miles away. Sometimes she hiked all night, from station to station on the Underground Railroad. Once she was hidden under blankets and vegetables in a farm wagon, and she rode through the night. Another time she was carried in a rowboat for miles.        She got toPennsylvaniaone morning just at sunrise. This story is mainly about   _  .
A. Harriet Tubman, the most famous conductor on the Underground Railroad
B. America's Underground Railroad System
C. how people in the United Statesused a secret network to help free slaves
D. why nearly 4,000,000 slaves arrived in the United States
Answer: