Boy does skateboard trick.
A boy is on a bicycle.
One can ride either a skateboard or a bicycle.
exists e1 x1 x2.(ne_nam_boy(x1) & Theme(e1,x2) & Actor(e1,x1) & v_skateboard(e1) & n_trick(x2))
exists p1 x1.(exists x2.(on(x1,x2) & n_bicycle(x2)) & n_boy(x1))