A man teaches a small class.
The man is teaching second grade.
Not all classes are a second grade class.
exists e1 s1 x1 x2.(Theme(e1,x2) & Actor(e1,x1) & v_teach(e1) & n_class(x2) & a_small(s1) & Theme(s1,x2) & n_man(x1))
exists e1 s1 x1 x2.(n_man(x1) & Theme(e1,x2) & Actor(e1,x1) & v_teach(e1) & n_grade(x2) & a_second(s1) & Theme(s1,x2))