A man and a woman sit on a bus, but not together.
People are riding the bus together.
While two people, here a man and a woman, can sit on the same bus, it doesn't mean they are together.
exists e1 x1 x2 x3 x4.(-exists e2 s1 x5 x6 x7.(a_together(s1) & Manner(e2,s1) & Actor(e2,x5) & v_sit(e2) & subset_of(x7,x5) & n_woman(x7) & subset_of(x6,x5) & n_man(x6)) & on(e1,x4) & n_bus(x4) & Actor(e1,x1) & v_sit(e1) & subset_of(x3,x1) & n_woman(x3) & subset_of(x2,x1) & n_man(x2))
exists e1 s1 x1 x2.(n_bus(x2) & a_together(s1) & Manner(e1,s1) & Theme(e1,x2) & Actor(e1,x1) & v_ride(e1) & n_people(x1))