A man teaches a classroom of children.
The man is teaching science.
A man can be teaching a classroom of children something other than science.
exists e1 x1 x2 x3.(Theme(e1,x2) & Actor(e1,x1) & v_teach(e1) & of(x2,x3) & n_child(x3) & n_classroom(x2) & n_man(x1))
exists e1 x1 x2.(n_man(x1) & Theme(e1,x2) & Actor(e1,x1) & v_teach(e1) & n_science(x2))