A person is riding his dirt bike.
A dirt bike sits on a trailer.
One can not be riding a dirt bike and sit on a trailer simultaneously
exists e1 x1 x2 x3.(Theme(e1,x2) & Actor(e1,x1) & v_ride(e1) & n_bike(x2) & of(x2,x3) & n_dirt(x3) & of(x2,x1) & n_male(x1) & n_person(x1))
exists e1 x1 x2 x3.(on(e1,x3) & n_trailer(x3) & Actor(e1,x1) & v_sit(e1) & n_bike(x1) & of(x1,x2) & n_dirt(x2))