A motorcyclist drives up the side of a green mountain while another bike remains stationary .
Chances are about even that a motorcyclist wearing a helmet drove up the side of a green mountain while another cyclist stayed behind because he did n't feel good .
Chances are about even that a motorcyclist wearing a helmet drove up the side of a green mountain while another cyclist stayed behind because he did n't feel good .
It is impossible that a motorcyclist wearing a helmet drove up the side of a green mountain while another cyclist stayed behind because he did n't feel good .
A motorcyclist wearing a helmet drove up the side of a green mountain while another cyclist stayed behind because he did n't feel good .