Extreme downhill mountain biking.
the bike rider on road
They are either on a road, or a mountain.
exists s1 x1 x2 x3 x4.(n_biking(x1) & a_.(s1) & Theme(s1,x1) & of(x1,x4) & n_mountain(x4) & of(x1,x3) & n_downhill(x3) & (x1 = x2) & ne_nam_extreme(x2) & a_topic(x1))
exists x1 x2 x3.(n_rider(x1) & of(x1,x2) & n_bike(x2) & a_topic(x1) & on(x1,x3) & n_road(x3))