A laughing baby in a walker.
A child laughing while sitting.
A laughing baby is a child laughing. Being in a walker requires sitting.
exists e1 x1 x2.(a_topic(x1) & in(x1,x2) & n_walker(x2) & n_baby(x1) & Actor(e1,x1) & v_laugh(e1))
exists e2 e1 x1 x2.(a_topic(x1) & while(e1,e2) & Actor(e2,x2) & v_sit(e2) & Actor(e1,x2) & v_laugh(e1) & (x1 = x2) & n_child(x1))