a woman returns the tennis ball.
A lady is having surgery.
One who is having a surgery wouldn't be returning a tennis ball.
exists e1 x1 x2 x3.(n_ball(x2) & of(x2,x3) & n_tennis(x3) & n_thing(e1) & Theme(e1,x2) & Actor(e1,x1) & v_return(e1) & n_woman(x1))
exists e1 x1 x2.(Theme(e1,x2) & Actor(e1,x1) & v_have(e1) & n_surgery(x2) & n_lady(x1))