A biker prepares to go down a hill.
The biker is on a unicycle.
Not all bikers ride a unicycle.
exists e1 p1 x1.(Topic(e1,p1) & Actor(e1,x1) & v_prepare(e1) & exists e2 s1 x2.(a_down(s1) & Manner(e2,s1) & Theme(e2,x2) & Actor(e2,x1) & v_go(e2) & n_hill(x2)) & n_biker(x1))
exists p1 x1.(n_biker(x1) & exists x2.(on(x1,x2) & n_unicycle(x2)))