Read this excerpt from Chapter 1 of Wheels of Change by Sue Macy. Some attribute the breakthrough to Ernest Michaux, a French carriage maker, though others credit Pierre Lallement, who worked for him. At any rate, the new velocipede was propelled by pedals and cranks attached directly to the axel of the front wheel, which was slightly larger than the wheel behind it. Forward progress could be stopped or slowed by pedaling backward. However, with iron tires and only an ineffective steel spring under the seat to absorb bumps in the road, this velocipede was a challenge to ride. It quickly earned the nickname "boneshaker."

Which signal word(s) from the excerpt suggest a change of direction?

a. some
b. at any rate
c. forward progress
d. however