a motocross rider gassing his bike.
The person is gassing a car.
A motorcross rider is a person. A bike is not a car.
exists e1 x1 x2 x3 x4.(a_topic(x1) & Theme(e1,x4) & Actor(e1,x3) & v_gas(e1) & n_bike(x4) & of(x4,x1) & n_male(x1) & (x1 = x3) & n_rider(x1) & of(x1,x2) & n_motocross(x2))
exists e1 x1 x2.(n_person(x1) & Theme(e1,x2) & Actor(e1,x1) & v_gas(e1) & n_car(x2))