A wet boy stands under an umbrella.
A boy shares his umbrella with his best friend.
A boy standing under an umbrella doesn't have to be sharing it with another person.  Therefore we cannot know that he shares his umbrella with his best friend.
exists e1 s1 x1 x2.(under(e1,x2) & n_umbrella(x2) & Actor(e1,x1) & v_stand(e1) & n_boy(x1) & a_wet(s1) & Theme(s1,x1))
exists e1 s1 x1 x2 x3.(with(e1,x3) & n_friend(x3) & r_most(s1) & a_good(s1) & Theme(s1,x3) & of(x3,x1) & n_male(x1) & n_male(x1) & Theme(e1,x2) & Actor(e1,x1) & v_share(e1) & n_umbrella(x2) & of(x2,x1) & n_boy(x1))