premise: A skateboarder in the air straddling his upside-down skateboard.
hypothesis: A skateboarder in a competition is in the air straddling his upside down skateboard.
explanation_1: Skateboarders do not need to be in a competition to do tricks. The first sentence does not indicate that he is competing.
explanation_2: Just because a skateboarder in the air straddling his upside-down skateboard, doesn't mean the skateboarder is in a competition.
explanation_3: Just because a skateboarder is performing tricks doesn't mean that he's in a competition.
premise_logic: exists e1 s1 x1 x2 x3 x4.(n_skateboard(x4) & a_upside-down(s1) & Theme(s1,x4) & of(x4,x2) & n_male(x2) & n_air(x2) & a_topic(x1) & in(x1,x2) & Theme(e1,x4) & Actor(e1,x3) & v_straddle(e1) & (x2 = x3) & n_skateboarder(x1))
hypothesis_logic: exists p1 x1 x2 x3 x5.(n_upside(x5) & of(x5,x3) & n_male(x3) & n_air(x3) & exists e1 x4 x6.(in(x1,x3) & Theme(e1,x5) & Actor(e1,x4) & v_straddle(e1) & down(x5,x6) & n_skateboard(x6) & (x3 = x4)) & in(x1,x2) & n_competition(x2) & n_skateboarder(x1))