A young man and an old woman are walking along a sidewalk next to a wall with graffiti on it .
It is certain that a man and his grandma walk together down a sidewalk past a wall .
Chances are about even that a man and his grandma walk together down a sidewalk past a wall .
It is certain that a man and his grandma walk together down a sidewalk past a wall .
A man and his grandma walk together down a sidewalk past a wall .