One biker wearing a helmet is jumping over an obstacle.
A biker is performing stunts.
Not every biker jumping over an obstacle is performing stunts.
exists e1 e2 s1 x1 x2 x3 x4.(a_over(s1) & Manner(e2,s1) & Theme(e2,x4) & Actor(e2,x1) & v_jump(e2) & n_obstacle(x4) & Theme(e1,x3) & Actor(e1,x2) & v_wear(e1) & n_helmet(x3) & (x1 = x2) & n_biker(x1) & card_eq_1(x1))
exists e1 x1 x2.(Theme(e1,x2) & Actor(e1,x1) & v_perform(e1) & n_stunt(x2) & n_biker(x1))