"Neither of" is used when the selection is only between two things where "none of" is used when there are a number of selections greater than two.
With either/neither always think 2.
That being said, the question is very poorly and ambiguously worded as "us" could easily mean any amount of people including 2. I am assuming the question wants you to answer B, however as a journey often takes many people. I would bring this up with your instructor, however, as such ambiguities get in the way of learning and understanding.
Hope this helps :)