A young girl going down a tube slide.
The boy is doing nothing.
Since there is both a boy and a girl, there are two different subjects.
exists e1 s1 s2 x1 x2 x3 x4.(a_topic(x1) & a_down(s2) & Manner(e1,s2) & Theme(e1,x3) & Actor(e1,x2) & v_go(e1) & n_slide(x3) & of(x3,x4) & n_tube(x4) & (x1 = x2) & n_girl(x1) & a_young(s1) & Theme(s1,x1))
exists x1.(n_boy(x1) & -exists e1 x2.(Theme(e1,x2) & Actor(e1,x1) & v_do(e1) & n_thing(x2)))