Who is riding on a skateboard?
The boy is riding on a skateboard.
    src        edge_attr  dst
0     3               on    7
1     3            above    4
2     3   to the left of   12
3     4   to the left of   12
4     7            below    8
5     8        riding on    3
6     8               on    3
7     8          wearing    6
8     8   to the left of   10
9     8      in front of   13
10   10  to the right of    8
11   12  to the right of    3
12   12               on    7
13   12  to the right of    4
14   13               on    9
15   13           behind    8