What of these best summarizes this passage?

Public awareness campaigns and festivals celebrating alternative forms of transportation helped increase the “cool factor,” but they have played a relatively small role. Most of the success has come from all three countries becoming a lot less car-friendly. Some cities have established car-free zones in the center, while others have become mazes of one-way streets, intersections with restricted turns, and sluggish speed zones. Many cities have also drastically reduced the available public parking to encourage people to leave their cars at home. Driving has become a headache, and alternative transportation has started to look more and more attractive.
a.
Other countries have managed to drive their cars less than the US.
c.
Cities are making it more difficult to park
b.
In order to make other modes of transportation even more convenient and appealing, driving a car needs to become less convenient and more of a hassle.
d.
none of these