person riding a bike doing a wheelie.
A boy stumbles on train tracks.
A boy cannot stumble on train tracks if the person is riding a bike.
exists e1 e2 x1 x2 x3 x4.(a_topic(x1) & for(e1,e2) & Theme(e2,x4) & Actor(e2,x2) & v_do(e2) & n_wheelie(x4) & Theme(e1,x3) & Actor(e1,x2) & v_ride(e1) & n_bike(x3) & (x1 = x2) & n_person(x1))
exists e1 x1 x2 x3.(on(e1,x2) & n_track(x2) & of(x2,x3) & n_train(x3) & Actor(e1,x1) & v_stumble(e1) & n_boy(x1))