People on a bridge look at the water.
People on a bridge look at the grass under the bridge.
There is either water or grass.
exists x1 x2 x3 x4.(n_water(x4) & a_topic(x1) & on(x1,x2) & at(x2,x4) & n_look(x2) & of(x2,x3) & n_bridge(x3) & n_people(x1))
exists x1 x2 x3 x4.(n_grass(x4) & a_topic(x1) & under(x1,x3) & n_bridge(x3) & n_bridge(x3) & on(x1,x2) & at(x2,x4) & n_look(x2) & of(x2,x3) & n_people(x1))