The biker is riding down a grassy mountainside.
The biker was on a ride with a group of friends.
The biker does not have to ride with a group of friends.
exists e1 s1 s2 x1 x2.(n_biker(x1) & a_down(s2) & Manner(e1,s2) & Theme(e1,x2) & Actor(e1,x1) & v_ride(e1) & n_mountainside(x2) & a_grassy(s1) & Theme(s1,x2))
exists p1 x1.(n_biker(x1) & exists x2 x3 x4.(on(x1,x2) & with(x2,x3) & of(x3,x4) & n_friend(x4) & n_group(x3) & n_ride(x2)))