The man on the bike is sitting on a gravel hill.
The man on the bike is sitting on the hill
The man is sitting on a gravel hill, means  the man is sitting on the hill.
exists e1 x1 x2 x3 x4.(n_bike(x2) & n_man(x1) & on(e1,x3) & n_hill(x3) & of(x3,x4) & n_gravel(x4) & Actor(e1,x1) & v_sit(e1) & on(x1,x2))
exists e1 x1 x2 x3.(n_hill(x3) & n_bike(x2) & n_man(x1) & on(e1,x3) & Actor(e1,x1) & v_sit(e1) & on(x1,x2))