People in a gymnasium dancing in a contest.
People in a gymnasium dancing and singing.
Dancing does not imply dancing and singing.
exists x1 x2 x3 x4.(a_topic(x1) & in(x1,x2) & in(x2,x4) & n_contest(x4) & n_dancing(x2) & of(x2,x3) & n_gymnasium(x3) & n_people(x1))
exists x1 x2 x3 x4 x5.(a_topic(x1) & in(x1,x2) & n_singing(x5) & n_dancing(x4) & subset_of(x5,x2) & subset_of(x4,x2) & of(x2,x3) & n_gymnasium(x3) & n_people(x1))