听力原文： The National Underground Railroad Freedom Center is a special museum. The Freedo

m Center is on the north side of the Ohio River. That is part of an area that meant hope for slaves trying to escape. It was called the "freedom corridor". Black people fleeing their owners could stand on the other side of the river and dream of freedom across the water.

The Freedom Center cost one hundred ten million dollars to build. Its collection shows two hundred objects. These include a copy of a wagon with a false bottom that was used to hide fleeing slaves. There are also photographs of Americans who were activists against slavery.

Visitors can also see objects from the Civil War. The southern states fought the northern states from eighteen sixty-one to eighteen sixty-five. In eighteen sixty-three, President Abraham Lincoln announced an order to free the slaves.

Perhaps the center's most interesting object is a small building where slaves were kept. This wooden "pen" stands two levels high. A slave trader built it in the eighteen thirties. People captured in Africa were temporarily forced to stay inside the pen. Then they were sold for service in places further south. The slave pen was found on a farm in the state of Kentucky. The owner of the farm gave it to the Freedom Center. Experts spent six years researching the history of the building.

Television star Oprah Winfrey introduces one of the films shown at the National Underground Railroad Freedom Center. Actors tell about a young woman who escapes slavery. She flees to a town called Ripley, Ohio. Her former owners try to recapture her. But a family active in the Underground Railroad helps her remain free.

What is The National Underground Railroad Freedom Center？

A．A concert hall.

B．A museum.

C．A zoo.

D．A theme park.