Sally started at the starting point.
She walked 10m forward. So far, she walked 10m, and she was 10m from the starting point.
Then she walked 5m backward. So far, she walked 15m, but she was only 5m from the starting point.
The distance she walked was 15m. But her displacement is how far she is from the starting point ... that's only 5m
Displacement = 5 meters
Distance = 15 meters
Displacement is 10m less than distance walked. <em>(B)</em>
===> If she kept going and walked <u><em>another </em></u>5m backward, she would be back where she started. The total distance she walked would be 20m, and her displacement would be zero !