Two skiers stand, two sit on slopes.
A man skates on a frozen lake.
A man cannot be present at the slope and frozen lake simultaneously.
exists e1 e2 x1 x2 x3.(on(e2,x3) & n_slope(x3) & Actor(e2,x2) & v_sit(e2) & n_thing(x2) & card_eq_2(x2) & Actor(e1,x1) & v_stand(e1) & n_skier(x1) & card_eq_2(x1))
exists e1 s1 x1 x2.(on(e1,x2) & n_lake(x2) & a_frozen(s1) & Theme(s1,x2) & Actor(e1,x1) & v_skate(e1) & n_man(x1))