The snowboarder is sitting down.
The snowboarder jumping in the air.
One cannot be simultaneously sitting and jumping.
exists e1 s1 x1.(n_snowboarder(x1) & a_down(s1) & Manner(e1,s1) & Actor(e1,x1) & v_sit(e1))
exists e1 x1 x2 x3.(n_air(x3) & n_snowboarder(x1) & a_topic(x1) & in(e1,x3) & Actor(e1,x2) & v_jump(e1) & (x1 = x2))