A biker jumps an obstacle.
A horse jumps a hurdle.
There is either a biker or a horse.
exists e1 x1 x2.(Theme(e1,x2) & Actor(e1,x1) & v_jump(e1) & n_obstacle(x2) & n_biker(x1))
exists e1 x1 x2.(Theme(e1,x2) & Actor(e1,x1) & v_jump(e1) & n_hurdle(x2) & n_horse(x1))