A motor Cross mountain bike racer is on a very bumpy ride.
a man is in a race with other on the mountain
Mountains aren't the only places where there would be a bumpy ride.
exists p1 x1 x2 x3 x4 x5.(exists s1 x6.(on(x1,x6) & n_ride(x6) & a_bumpy(s1) & Theme(s1,x6) & r_very(x6)) & n_racer(x1) & of(x1,x5) & n_bike(x5) & of(x1,x4) & n_mountain(x4) & (x1 = x3) & ne_nam_cross(x3) & of(x1,x2) & n_motor(x2))
exists p1 x1 x4.(n_mountain(x4) & exists x2 x3.(in(x1,x2) & on(x2,x4) & with(x2,x3) & n_other(x3) & n_race(x2)) & n_man(x1))