the two boys playing guitar
The two boys play a folk song on guitar.
The boys do not have to be playing a folk song.
exists e1 x1 x2 x3.(n_boy(x1) & card_eq_2(x1) & a_topic(x1) & Theme(e1,x3) & Actor(e1,x2) & v_play(e1) & n_guitar(x3) & (x1 = x2))
exists e1 x1 x2 x3 x4.(n_boy(x1) & card_eq_2(x1) & on(e1,x4) & n_guitar(x4) & Theme(e1,x2) & Actor(e1,x1) & v_play(e1) & n_song(x2) & of(x2,x3) & n_folk(x3))