The Underground Railroad is not a railroad that is underground, instead, it is referring to a secret passage for slave escaping in safe houses. The conductor of the Underground Railroad could be the person who helps the slave escape, the lines could refer to the road or the passage which the slaves escaped from one safe house to another, the station could refer to the stops they make in the safe houses, and the freight may refer to the slaves that are escaping.
Your answer is B: A Bill of Rights and an announcement they would establish a republic based upon hope this helps :D
