A person is riding a dune buggy up a sandy hill.
A person is in a dune buggy race going up a hill.
Just because a person is riding a dune buggy up a sandy hill does not imply that they are in a dune buggy race.
exists e1 s1 x1 x2 x3 x4.(up(e1,x4) & n_hill(x4) & a_sandy(s1) & Theme(s1,x4) & Theme(e1,x2) & Actor(e1,x1) & v_ride(e1) & n_buggy(x2) & of(x2,x3) & n_dune(x3) & n_person(x1))
exists p1 x1.(exists e1 s1 s2 x2 x3 x4 x5.(in(x1,x2) & n_hill(x5) & Time(e1,x5) & a_up(s2) & Manner(e1,s2) & Actor(e1,x4) & v_go(e1) & (x2 = x4) & n_race(x2) & of(x2,x3) & n_buggy(x3) & a_dune(s1) & Theme(s1,x2)) & n_person(x1))