The boy is jumping in the air.
The boy jumps in air to keep from stepping on a pebble.
A boy can jump in the air without trying to avoid stepping on a pebble.
exists e1 x1 x2.(n_air(x2) & n_boy(x1) & in(e1,x2) & Actor(e1,x1) & v_jump(e1))
exists e1 p1 x1 x2.(n_boy(x1) & in(e1,x2) & Topic(x2,p1) & exists e3 e2 x3 x4.(from(e2,e3) & on(e3,x4) & n_pebble(x4) & Actor(e3,x3) & v_step(e3) & Actor(e2,x2) & v_keep(e2)) & n_air(x2) & Actor(e1,x1) & v_jump(e1))