A surfer rides on a very rough wave.
A surfer is riding a big wave.
Because a surfer rides a very rough wave, the wave must be big.
exists e1 s1 x1 x2.(on(e1,x2) & n_wave(x2) & a_rough(s1) & Theme(s1,x2) & r_very(x2) & Actor(e1,x1) & v_ride(e1) & n_surfer(x1))
exists e1 s1 x1 x2.(Theme(e1,x2) & Actor(e1,x1) & v_ride(e1) & n_wave(x2) & a_big(s1) & Theme(s1,x2) & n_surfer(x1))