A motocross rider, riding along a dirt track on a sunny day.
The rider goes nearly 50 miles an hour
The speed of the motocross rider - 50 miles an hour, nearly - is not known from the first sentence, we just know they are riding.
exists e1 s1 x1 x2 x3 x4 x5 x6.(a_topic(x1) & on(e1,x6) & n_day(x6) & a_sunny(s1) & Theme(s1,x6) & along(e1,x4) & n_track(x4) & of(x4,x5) & n_dirt(x5) & Actor(e1,x3) & v_ride(e1) & (x1 = x3) & n_rider(x1) & of(x1,x2) & n_motocross(x2))
exists x1.(n_rider(x1) & all x2.(n_hour(x2) -> exists e1 x3.(Theme(e1,x3) & Actor(e1,x1) & v_go(e1) & for(x3,x2) & n_mile(x3) & card_eq_50(x3) & r_nearly(x3))))