Fugitive slaves traveled to pennsylvania using all of the following methods except?

о wagons.
о railroads.
о slave ships.
о walking

Well, this is very easy, first up; what's a fugitive?

A fugitive is a person that has escaped a place/or is in hiding;to avoid arrest/persecution.

So traveling by wagons,railroads,and walking makes sense. Except for one, slave ships, that makes no sense at all. Why would fugitive slaves travel on "slave ships?"

Slave ships-orginally slaves where brought to the americas via slave ships