A person stunt riding on a BMX type of bicycle.
A person riding
Stunt riding is a type of riding,
exists x1 x2 x3 x4 x5.(a_topic(x1) & on(x1,x3) & of(x3,x5) & n_bicycle(x5) & n_type(x3) & (x3 = x4) & ne_org_bmx(x4) & n_stunt(x1) & Time(x1,x2) & n_riding(x2) & n_person(x1))
exists x1 x2.(a_topic(x1) & Time(x1,x2) & n_riding(x2) & n_person(x1))