A person rides a four wheeled vehicle on sand dunes.
Four wheeling on the sand dunes.
A person is driving a four wheeler on sand dunes, so they are four wheeling on sand dunes.
exists e1 s1 x1 x2 x3 x4.(Theme(e1,x2) & Actor(e1,x1) & v_ride(e1) & on(x2,x3) & n_dune(x3) & of(x3,x4) & n_sand(x4) & n_vehicle(x2) & a_wheeled(s1) & Theme(s1,x2) & card_eq_4(x2) & n_person(x1))
exists x1 x2 x3.(n_dune(x2) & of(x2,x3) & n_sand(x3) & a_topic(x1) & on(x1,x2) & n_wheeling(x1) & card_eq_4(x1))