An aspirin added to the water would preserve the flowers.
This vase of flowers will stay fresher if an aspirin is added to the water.
The flowers could not be in a vase. There are other ways to hold flowers.
exists e2 e1 x1 x2 x3 x4.(n_flower(x4) & n_water(x2) & to(e1,x2) & Theme(e2,x4) & Actor(e2,x3) & v_preserve(e2) & (x2 = x3) & Actor(e1,x1) & v_add(e1) & n_aspirin(x1))
exists x2 x3.(n_vase(x3) & n_water(x2) & all x1 e1.((to(e1,x2) & Theme(e1,x1) & v_add(e1) & n_aspirin(x1)) -> exists e2 p1 x4.(exists s1.(r_more(s1) & Theme(s1,x3) & a_fresher(s1)) & Topic(e2,p1) & Actor(e2,x3) & v_stay(e2) & of(x3,x4) & n_flower(x4))))