A group of four boys plays with mud in the water and grass.
Boys are getting their clothes dirty.
Boys doesn't imply exactly four boys.  Just because they are playing in mud, doesn't imply they will get their clothes dirty.
exists e1 x1 x2 x3 x4 x5 x6.(n_water(x5) & with(e1,x3) & subset_of(x6,x3) & n_grass(x6) & subset_of(x4,x3) & in(x4,x5) & n_mud(x4) & Actor(e1,x1) & v_play(e1) & of(x1,x2) & n_boy(x2) & card_eq_4(x2) & n_group(x1))
exists e1 x1 x2 x3.(Theme(e1,x2) & Actor(e1,x1) & v_get(e1) & n_dirty(x2) & of(x2,x3) & n_clothes(x3) & of(x2,x1) & n_thing(x1) & n_boy(x1))