A boy grinds a ledge on his skateboard .
There is a better than even chance that a boy grinds a ledge on his skateboard and falls .
There is a better than even chance that a boy grinds a ledge on his skateboard and falls .
There is almost no chance that a boy grinds a ledge on his skateboard and falls .
A boy grinds a ledge on his skateboard and falls .