A person on a tricycle.
The man is riding on a bicycle.
A tricycle has 3 wheels a bicycle has 2.
exists x1 x2.(a_topic(x1) & on(x1,x2) & n_tricycle(x2) & n_person(x1))
exists e1 x1 x2.(n_man(x1) & on(e1,x2) & n_bicycle(x2) & Actor(e1,x1) & v_ride(e1))