People riding on a vehicle that is being pulled by another person down a street by the beach.
The people must not know that car surfing is a very dangerous practise.
People can car surf while knowing it is a dangerous practice.
exists e1 e2 x1 x2 x3 x4 x5 x6 x7 x8.(n_beach(x8) & n_person(x5) & a_topic(x1) & on(e1,x3) & Actor(e2,x8) & Actor(e2,x6) & down(x6,x7) & n_street(x7) & n_person(x6) & -(x6 = x5) & Theme(e2,x4) & v_pull(e2) & (x3 = x4) & n_vehicle(x3) & Actor(e1,x2) & v_ride(e1) & (x1 = x2) & n_people(x1))
exists x1.(n_people(x1) & -exists e1 p1.(exists e2 p2.(Topic(e2,p2) & Actor(e2,x1) & v_know(e2) & exists p3 x2 x3.(exists s1 x4.((x2 = x4) & n_practise(x4) & a_dangerous(s1) & Theme(s1,x4) & r_very(x4)) & n_surfing(x2) & of(x2,x3) & n_car(x3))) & Topic(e1,p1) & Actor(e1,x1) & v_must(e1)))